Automated peritoneal dialysis system using stepper motor

ABSTRACT

An embodiment of a peritoneal dialysis system includes an enclosure, a door hingedly attached to the enclosure, a stepper motor housed by the enclosure, a solid pump piston in operable communication with the stepper motor and including a solid pump shaft attached to or integrally formed with a solid pump head, and a disposable unit contacting the enclosure and the door. The disposable unit includes a moveable membrane operable with the solid pump head. The stepper motor is configured to move the solid pump head towards and away from the disposable unit. The system further includes a position detection apparatus operable with the stepper motor and located to provide an output indicative of a position of the solid pump head relative to a reference position.

PRIORITY CLAIM

This application claims priority to and the benefit as a continuation ofU.S. patent application Ser. No. 13/661,420, entitled “Method ofOperating A Disposable Pumping Unit”, filed Oct. 26, 2012, which is acontinuation application of U.S. patent application Ser. No. 11/617,536,entitled, “Method of Making A Peritoneal Dialysis Therapy Machine”,filed Dec. 28, 2006, now U.S. Pat. No. 8,298,170, issued Oct. 30, 2012,which is a continuation application of U.S. patent application Ser. No.10/155,384, entitled, “Disposable Medical Fluid Unit Having RigidFrame,” filed May 24, 2002, now U.S. Pat. No. 7,175,606, issued Feb. 13,2007, the entire contents of each of which are incorporated herein byreference and relied upon.

BACKGROUND OF THE INVENTION

The present disclosure generally relates to dialysis systems. Morespecifically, the present disclosure relates to automated peritonealdialysis systems. The present disclosure also relates to methods ofperforming automated peritoneal dialysis and devices for performingsame.

Due to disease, insult or other causes, a person's renal system canfail. In renal failure of any cause, there are several physiologicalderangements. The balance of water, minerals and the excretion of dailymetabolic load is no longer possible in renal failure. During renalfailure, toxic end products of nitrogen metabolism (urea, creatinine,uric acid, and others) can accumulate in blood and tissues.

Kidney failure and reduced kidney function have been treated withdialysis. Dialysis removes waste, toxins and excess water from the bodythat would otherwise have been removed by normal functioning kidneys.Dialysis treatment for replacement of kidney functions is critical tomany people because the treatment is life saving. One who has failedkidneys could not continue to live without replacing at least thefiltration functions of the kidneys.

Hemodialysis and peritoneal dialysis are two types of dialysis therapiescommonly used to treat loss of kidney function. Hemodialysis treatmentutilizes the patient's blood to remove waste, toxins and excess waterfrom the patient. The patient is connected to a hemodialysis machine andthe patient's blood is pumped through the machine. Catheters areinserted into the patient's veins and arteries to connect the blood flowto and from the hemodialysis machine. As blood passes through a dialyzerin the hemodialysis machine, the dialyzer removes the waste, toxins andexcess water from the patient's blood and returns the blood back to thepatient. A large amount of dialysate, for example about 120 liters, isused to dialyze the blood during a single hemodialysis therapy. Thespent dialysate is then discarded. Hemodialysis treatment lasts severalhours and is generally performed in a treatment center about three orfour times per week.

Peritoneal dialysis utilizes a dialysis solution or “dialysate”, whichis infused into a patient's peritoneal cavity through a catheterimplanted in the cavity. The dialysate contacts the patient's peritonealmembrane in the peritoneal cavity. Waste, toxins and excess water passfrom the patient's bloodstream through the peritoneal membrane and intothe dialysate. The transfer of waste, toxins, and water from thebloodstream into the dialysate occurs due to diffusion and osmosis,i.e., an osmotic gradient occurs across the membrane. The spentdialysate drains from the patient's peritoneal cavity and removes thewaste, toxins and excess water from the patient. This cycle is repeated.

There are various types of peritoneal dialysis therapies, includingcontinuous ambulatory peritoneal dialysis (“CAPD”), automated peritonealdialysis and continuous flow peritoneal dialysis. CAPD is a manualdialysis treatment, in which the patient connects an implanted catheterto a drain and allows a spent dialysate fluid to drain from theperitoneal cavity. The patient then connects the catheter to a bag offresh dialysate and manually infuses fresh dialysate through thecatheter and into the patient's peritoneal cavity. The patientdisconnects the catheter from the fresh dialysate bag and allows thedialysate to dwell within the cavity to transfer waste, toxins andexcess water from the patient's bloodstream to the dialysate solution.After a dwell period, the patient repeats the manual dialysis procedure.

In CAPD the patient performs several drain, fill, and dwell cyclesduring the day, for example, about four times per day. Each treatmentcycle typically takes about an hour. Manual peritoneal dialysisperformed by the patient requires a significant amount of time andeffort from the patient. This inconvenient procedure leaves ample roomfor improvement and therapy enhancements to improve patient quality oflife.

Automated peritoneal dialysis (“APD”) is similar to CAPD in that thedialysis treatment includes a drain, fill, and dwell cycle. APDmachines, however, automatically perform three to four cycles ofperitoneal dialysis treatment, typically overnight while the patientsleeps. The APD machines fluidly connect to an implanted catheter. TheAPD machines also fluidly connect to a source or bag of fresh dialysateand to a fluid drain.

The APD machines pump fresh dialysate from the dialysate source, throughthe catheter, into the patient's peritoneal cavity and allow thedialysate to dwell within the cavity so that the transfer of waste,toxins and excess water from the patient's bloodstream to the dialysatesolution can take place. The APD machines then pump spent dialysate fromthe peritoneal cavity, though the catheter, to the drain. APD machinesare typically computer controlled so that the dialysis treatment occursautomatically when the patient is connected to the dialysis machine, forexample, when the patient sleeps. That is, the APD systems automaticallyand sequentially pump fluid into the peritoneal cavity, allow for adwell, pump fluid out of the peritoneal cavity and repeat the procedure.

As with the manual process, several drain, fill, and dwell cycles willoccur during APD. A “last fill” is typically used at the end of APD,which remains in the peritoneal cavity of the patient when the patientdisconnects from the dialysis machine for the day. APD frees the patientfrom having to manually performing the drain, dwell, and fill steps.

However, continuing needs exist to provide improved APD systems. Forexample, needs exist to provide simplified APD systems that are easierfor patients to use and operate. Further, needs exist to provide lowercost APD systems and APD systems which are less costly to operate.Particularly, needs exist to clinically, economically and ergonomicallyimprove known APD systems.

APD systems need to be improved for home use. One common problem withcurrent home systems is that they are susceptible to electrical shockdue to “leakage current”. Current that flows from or between conductorsinsulated from one another and from earth is called “leakage current”.If any conductor is raised to a potential above earth potential, thensome current is bound to flow from that conductor to earth. This is trueeven of conductors that are well insulated from earth, since there is nosuch thing as perfect insulation or infinite resistance. The amount ofcurrent that flows depends on: (i) the potential, (ii) the capacitatereactance between the conductor and earth and (iii) the resistancebetween the conductor and earth.

For medical equipment, several different leakage currents are definedaccording to the paths that the leakage currents take. An “earth leakagecurrent” is the current which normally flows in the earth conductor of aprotectively earthed piece of equipment. In medical equipment, impedanceto earth from an enclosure is normally much lower through a protectiveearth conductor than it is through the patient. However, if theprotective earth conductor becomes open circuited, the patient could beat risk of electrical shock.

“Patient leakage current” is the leakage current that flows through apatient connected to an applied part or parts. It can either flow fromthe applied parts via the patient to earth or from an external source ofhigh potential via the patient and the applied parts to earth. Othertypes of leakage currents include “enclosure leakage current”, and“patient auxiliary current”.

Leakage currents are normally small, however, the amount of currentrequired to produce adverse physiological effects in patients is alsosmall. Accordingly, leakage currents must be limited as much as possibleby the design of the equipment and be within safety limits.

SUMMARY OF THE INVENTION

Generally, the present disclosure provides improved dialysis systems andimproved methods of performing dialysis. More particularly, the presentdisclosure provides systems and methods for performing automatedperitoneal dialysis (“APD”). The systems and methods of the presentdisclosure automatically provide dialysis therapy by providing dialysisfluid to the patient and draining spent dialysis fluid from the patient.

Also, the systems and methods of the present disclosure can performvarious dialysis therapies. One example of a dialysis therapy which canbe performed according to the present disclosure includes an automaticdialysis fluid exchange of a patient fill, dwell and a patient drain.The dialysis system of the present disclosure can automatically performdialysis therapy on a patient, for example, during nighttime while thepatient sleeps.

To this end, in an embodiment a dialysis system is provided. The systemincludes a fluid supply line. A disposable unit is in fluidcommunication with the fluid supply line. The disposable unit has atleast two flexible membranes that bond together at selected locationsand to a rigid plastic piece or manifold. The membranes can be single ordouble layer. One suitable membrane material is described herein. Themembranes seal to one another so as to define a fluid pump receptacleand a fluid heating pathway. The membranes and plastic manifold define anumber of flexible valve chambers. The disposable unit also fluidlycommunicates with a patient line and a drain line.

The manifold and other areas of the disposable unit include reduced ortapered edges that provide an area to seal the membranes. The reducedthickness or tapered area requires less heat than the full thickness,which reduces the heat sinking disparity between the thickness of themanifold of the disposable unit and the thinner flexible membranes. Theframe of the manifold is bowed or curved to provide rigidity. The frameis also asymmetrical and designed to be placed into the hardware unit inonly one direction.

The hardware unit can be manually transported to a patient's home andopened so that the patient can place a disposable unit therein andclosed so that the dialysis unit and the disposable unit cooperativelyform a pump chamber that enables dialysis fluid to be pumped to and fromthe patient. The hardware unit has an enclosure that defines a pumpshell, a valve actuator and a heater. The disposable unit is placed inand removed from the enclosure. The fluid pump receptacle of thedisposable unit and the shell of the hardware unit form a pump chamber.The pump chamber operates with a pump actuator, which is also locatedinside the transportable hardware unit.

When packaged, a plurality of tubes extend from the disposable unit. Theends of the tubes have connectors that attach to a single body. The bodydefines or provides a plurality of tip protectors that hold the tubes inan order according to steps of the therapy. The body is configured toslide into the hardware unit of the system from one direction, so that apatient can readily pull the tubes and connectors from the tip protectororganizer.

The tip protector used to house the patient fluid connector includes ahydrophobic filter that allows air but not fluid to escape. This ventedtip protector enables the system to be primed without having to performelevation balancing or controlled fluid metering. The system performs aprime by flowing fluid through the system and into the patient fluidline until the dialysate backs up against the filter, causing a fluidpressure increase, which is sensed by the system. The system then stopsthe pump.

The hardware unit also provides a controller. The controller includes aplurality of processors, a memory device for each processor andinput/output capability. One of the processors coordinates operation ofthe pump actuator, the valve actuator and the heater with the variousstages of dialysate flow, such as the fill, dwell and drain stages. Theprocessor also controls or obtains feedback from a plurality ofdifferent types of sensors. The sensors include, among others, acapacitance fluid volume sensor, a dialysis fluid temperature sensor, apressure sensor, a vacuum sensor, an air detection sensor and amechanical positioning sensor.

In an embodiment, the system uses both preset motion control andadaptive pressure control to control the pressure of fluid within thepump receptacle. The system uses a preset pump motor acceleration toovercome system compliance (i.e., membrane and tubing expansion), whichwould not otherwise be readily overcome by known proportional,differential or integral control. After the system overcomes compliance,the system converts to an adaptive control using adaptive techniques forcontrolling pressure by precisely controlling the velocity of a pumpmotor shaft. The adaptive parameters are modified over time to fine tunethe system. This method is especially important for the patient fill anddrain cycles, wherein the patient can feel pressure fluctuations. Themethod also readily compensates for pressure variations due to bagheight, bag fullness, etc.

The capacitance fluid volume sensor indicates a volume of fluid in thepump chamber, wherein the sensor generates a voltage signal that isindicative of the volume of fluid in the receptacle. The controllerreceives the voltage signal and converts the signal into an amount offluid or an amount of air within the flexible fluid receptacle of thepump chamber.

The pump actuator can be mechanically or pneumatically operated. Whenmechanically driven, a pump motor drives a vacuum source, such as apiston-cylinder, which pulls a vacuum on the membranes of the fluidreceptacle of the disposable unit. Here, a mechanical positioningsensor, such as an encoder, senses the angle of a pump motor shaftrelative to a home position and sends a signal to the controller,wherein the controller can adjust the pump motor accordingly. Theencoder also provides safety feedback to the controller, whereby thecontroller, once therapy starts, prevents the camshaft from rotating toa position where the valves can free fill the patient. When the pumpactuator is pneumatically operated, the system in an embodiment uses avacuum pump to pull apart the membranes of the fluid receptacle. Here,the system uses a vacuum sensor to sense the state of the vacuum pumpand a mechanical sensing device, such as a linear encoder, to sense thestate of a pump piston.

Thus, in an embodiment, the system maintains a negative pressure on oneof the membranes of the fluid receptacle of the disposable unit to pullsame away from the other membrane and draw dialysis fluid into the fluidreceptacle. The negative pressure on the active membrane is thenreleased, which pushes the membrane towards the other membrane anddispels the dialysis fluid from the pump receptacle. In anotherembodiment, a mechanical pump piston can be pneumatically attached toone of the membranes, wherein the system mechanically pulls the membraneaway from the other membrane. In an embodiment, the membrane is coupledto the pump piston through negative pressure. The pump also includes adiaphragm that is pulled to a bottom side of the piston head, whereinthe membrane is pulled to a top side of same. In a further embodiment,the system mechanically pushes one of the membranes while applying thenegative pressure to same.

The system also performs other necessary tasks automatically. Forexample, the system automatically heats the dialysate to a desiredtemperature while pumping dialysate to the patient. The heater heats thefluid heating pathway defined by the flexible membranes of thedisposable unit. In an embodiment, the heater includes an electricalheating plate. Alternatively, or in addition to the heating plate, theheater includes an infrared heating source. In an embodiment, the fluidheating pathway and the heater define an in-line heater that heatsdialysate as it travels from the supply bag to the patient.

The system employs a method of heat control that uses a knowledge-basedalgorithm and a fuzzy logic based algorithm. The former uses laws ofphysics, empirical data and sensed inputted signals. The latter inputs adifference between desired and actual temperatures and uses fuzzy logicmembership functions and fuzzy logic rules. Each algorithm operates at adifferent update frequency. Each algorithm outputs a duty cycle, whereinthe system weights the fuzzy logic based duty cycle relative to theknowledge based duty cycle and produces an overall heater control dutycycle. This method enables accurate dialysate temperature control.

The system automatically purges air from the dialysate, for example,through the pump chamber. The system also senses a total volume of fluidpumped to the patient, records and logs same. Furthermore, the systemknows the instantaneous flow rate and fluid pressure of fluid enteringor leaving the patient's peritoneal cavity.

The disposable unit includes a valve manifold. The manifold defines aplurality of valve chambers. The hardware unit includes a valve actuatorthat selectively and sequentially presses against one or more of thevalve chambers. In an embodiment, a mechanically operated valve actuatorincludes a single camshaft and a plurality of cams. The cams pressagainst one of the membranes of the disposable unit to engage the othermembrane and block or disallow fluid flow. As stated above, the systemuses a sensing device, such as a rotary encoder, to sense the angle ofthe camshaft relative to a home position, so that the controller canrotate the camshaft to open or close one or more valves as desired. Thesingle camshaft toggles back and forth between: supply and pump chamberfill positions; patient drain and system drain positions; and betweenpump chamber fill and patient fill positions. These positions areactuated by a unique rotational position on an overall cam profile(i.e., the superposition of each of the individual cams as seen from theend of the camshaft).

The disposable unit of the present disclosure is provided in a varietyof different forms. In an embodiment, the portion of the disposable unitforming the heating path is formed by the same membranes that seal tothe rigid member or manifold that forms the valve chambers. The samemembranes also form the pump receptacle. In another embodiment, thedisposable unit includes a first set of membranes that form the pumpreceptacle and the valve manifold via the rigid member. Here, thedisposable unit includes a second set of membranes, distinct from thefirst membranes, which form the fluid heating path. In an embodiment,medical grade tubing connects the first set of membranes to the secondset. In particular, the tubing enables the fluid heating path to fluidlyconnect to the valve manifold.

The disposable unit in another embodiment includes a first flexiblemembrane and a second flexible membrane that house the pump receptacle,the fluid heating path and the rigid valve manifold. The disposable unitalso includes a rigid frame that attaches to at least one of the firstand second flexible membranes. The rigid frame enables a patient oroperator to place the frame and the disposable unit into the enclosureof the hardware unit of the automated dialysis system. The rigid frameis sized to securely fit into a dedicated place in the enclosure. Therigid frame further holds the disposable unit stable while the patientor operator connects tubes to same. For example, the valve manifoldprovides ports or other types of connectors for connecting to a supplyline, a drain line and a patient line. In an embodiment, the rigid frameextends around or circumvents the membranes including the pumpreceptacle, fluid heating path and valve manifold. In an embodiment, therigid frame is plastic. In an embodiment, the rigid frame is bowed alongat least two sides to increase the rigidly of the disposable unit and tokeep the disposable unit from deforming during the heat sealing portionof its manufacture.

In an embodiment, the rigid member or manifold of the disposable unitincludes interfaces that allow the membranes to be more easily sealed tothe manifold. The manifold edges are tapered to reduce the heat neededto form a cohesive bond between the membranes and the plastic valvemanifold. The knife-like tapered edges also reduce or eliminate the gapbetween the top and bottom membranes, which minimizes the opportunityfor leaks to occur in the disposable unit. The chamfered edges alsoreduce the likelihood that the heat sealing process will burn throughthe membranes.

The hardware unit described above includes a display device thatprovides dialysis system information. The display device also enablesthe patient or operator to enter information and commands into thecontroller. For example, the display device can include an associatedtouch screen that enables the patient or operator to initiate automaticflow of the dialysate through the disposable unit. The system begins topneumatically and/or mechanically pump dialysate through the pumpchamber, past the in-line heater and into the patient's peritonealcavity. Thereafter, the system automatically runs the other cycles ofdialysis therapy, for example, while the patient sleeps and/or at night.The automated system not only transfers dialysate from a supplycontainer to the patient, the system allows the dialysate to dwellinside the patient for an amount of time and automatically operates totransfer the dialysate from the patient to a drain.

The system provides a graphical user interface (“GUI”). The GUI in anembodiment employs an embedded web browser and an embedded web server.The web browser and server operate on a main microprocessor for thesystem. The GUI also employs instrument access and control software,which operates on the main system processor and on one or more delegateprocessors. The instrument access and control software controls lowerlevel devices, such as the heater and the pump. The GUI also providesintermediate software that allows the web browser to communicate withthe instrument access and control software.

The GUI displays a number of therapy set-up screens and a number ofdialysis treatment screens. The set-up screens generally walk thepatient through the set-up portion of the therapy. The system waits foran operator input before proceeding to the next set-up screen. Theset-up screens provide information to the patient in the form ofreal-life images of the equipment and through animations of the actionsneeded to connect the system to the patient.

The therapy treatment screens display the various cycles of the therapyto the patient in real-time or substantially in-real time. The therapytreatment screens display information such as cycle time in both agraphical and quantitative manner. The therapy treatment screens do notrequire input from a patient, who may be sleeping while these screensare displayed. When the therapy is complete, the system once againdisplays a number of disconnection screens which, like the set-upscreens, wait for an input from the patient before performing an action.

The treatment screens are colored and lighted for night time viewing,and may be easily seen from a distance of about ten to fifteen feet,however, the screens are lighted so as not to wake a sleeping patient.In an embodiment, the background of the screens is black, while thegraphics are ruby red. In contrast, the set-up screens are lighted andcolored for daytime viewing.

With the above embodiments, one advantage of the present disclosure isto provide improved systems and methods for performing dialysis.

Another advantage of the present disclosure is to provide improvedsystems and methods for performing peritoneal dialysis.

A further advantage of the present disclosure is to provide an automatedperitoneal dialysis system and method of operating same.

Still another advantage of the present disclosure is to provide anautomated peritoneal dialysis system that provides dialysis therapyadvantages.

Still a further advantage of the present disclosure is to provide anautomated peritoneal dialysis system that has economic advantages.

Yet another advantage of the present disclosure is to provide anautomated peritoneal dialysis system that has quality of lifeadvantages.

A still further advantage of the present disclosure is to provide adisposable unit having bowed sides, which increase rigidity and decreaseflexing of disposable unit.

Moreover, an advantage of the present disclosure is to provide adisposable unit having tapered interfaces that decrease the heat sinkingof the semi-rigid manifold and provide a more robust seal.

Various features and advantages of the present disclosure can becomeapparent upon reading this disclosure including the appended claims withreference to the accompanying drawings. The advantages may be desired,but not necessarily required to practice the present invention.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 schematically illustrates an embodiment of an automated dialysissystem of the present disclosure having a mechanically actuated fluidpump.

FIG. 2 schematically illustrates another embodiment of an automateddialysis system of the present disclosure having a fluidly actuatedfluid pump.

FIGS. 3A and 3B illustrate perspective views of the hardware unit anddisposable unit of the present disclosure.

FIG. 4A is a plan view of one embodiment of the hardware and disposableunits of the present disclosure.

FIG. 4B is a cross-sectional view taken along line 4B-4B in FIG. 4A,which shows one possible configuration of the system components withinthe hardware unit.

FIGS. 5 and 6 illustrate additional embodiments of the disposable unitof the present disclosure.

FIG. 7 is a perspective view of one embodiment of a valve manifold thatincludes a reduced thickness interface for sealing to membranes of adisposable dialysis unit.

FIG. 8 is a perspective view of one embodiment of a multiple tipprotector organizer of the present disclosure.

FIG. 9 is an elevation sectional view of the multiple tip protectororganizer illustrated in FIG. 8.

FIG. 10 is an elevation sectional view of one embodiment of a vented tipprotector of the present disclosure showing the tip protector housing apatient fluid line connector.

FIG. 11 is an elevation sectional view of one embodiment of the patientfluid line connector that couples to the vented tip protector of thepresent disclosure.

FIG. 12 is an elevation sectional view of one embodiment of the ventedtip protector of the present disclosure.

FIG. 13 is a sectional view of one embodiment of a single layer filmstructure for the disposable unit membranes of the present disclosure.

FIG. 14 is a sectional view of one embodiment of a multiple layer filmstructure for the disposable unit membranes of the present disclosure.

FIG. 15 is a perspective view of one embodiment of a valve actuator incombination with the fluid manifold of the present disclosure.

FIGS. 16A and 16B illustrate features of the camshaft and camarrangement of the present disclosure.

FIGS. 17A and 17B illustrate an embodiment of a mechanically operatedfluid pump and capacitance type fluid volume sensor of the presentdisclosure.

FIG. 18 illustrates an alternate embodiment of a fluidly operated fluidpump and capacitance sensor of the present disclosure.

FIG. 19 is a graphical illustration of one embodiment of the presentdisclosure for the control of the pressure inside a fluid pump throughprecise velocity control of a pump piston.

FIG. 20 is a schematic illustration of one embodiment of an algorithm ofthe present disclosure for performing proportional, integral andderivative type adaptive pressure control.

FIG. 21 is a graphical illustration of one embodiment of the presentdisclosure for the control of the pressure inside a fluid pump duringrepeated patient fill and pull from supply bag strokes.

FIG. 22 is a graphical illustration of one embodiment of the presentdisclosure for the control of the pressure inside a fluid pump duringrepeated patient drain and pump to drain strokes.

FIG. 23 is a schematic illustration of one embodiment of an algorithm ofthe present disclosure for adapting pressure error correction parametersover time to optimize pressure control efficiency.

FIG. 24 is a table illustrating one set of the correction parametersillustrated in connection with FIG. 23.

FIG. 25 is a schematic representation of one embodiment of a heatercontrol method of the present disclosure.

FIG. 26 is a flow diagram of a knowledge based algorithm of the methoddiscussed in connection with FIG. 25.

FIG. 27 is a flow diagram of a fuzzy logic based algorithm of the methoddiscussed in connection with FIG. 25.

FIG. 28 is an electrical insulation diagram illustrating one embodimentfor providing double electrical insulation in the medical fluid unit ofthe present disclosure.

FIG. 29 is a schematic representation of one embodiment of the web basedgraphical user interface of the present disclosure.

FIGS. 30A to 30M are screen shots from a display device employing thegraphical user interface of the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

The present disclosure relates to dialysis systems and methods ofperforming dialysis. In particular, the present disclosure relates to asystem and method for automatically providing peritoneal dialysistherapy to patients. The present disclosure provides automatic multipleexchanges of dialysis fluid to and from the patient's peritoneal cavity.The automatic exchanges of dialysate include drain, fill, and dwellperiods, which usually occur while the patient sleeps. A typical therapycan include three to five exchanges of dialysis fluid. The presentdisclosure, in an embodiment, provides a single pass system, wherein thedialysate passes through the peritoneal cavity only once before beingdisposed. While the present disclosure performs peritoneal dialysis, itis also suitable for other types of dialysis and other medical fluidtransfer operations.

I. The System Generally

Referring now to the drawings and in particular to FIG. 1, a typicaltherapy performed by the system 10 of the present disclosure begins bydraining dialysis solution that is already in the patient's peritonealcavity 12. The system 10 pumps fresh dialysate from one of a pluralityof supply bags 14, through an in-line heater 16 to the patient orperitoneal cavity 12. After a dwell period in the peritoneal cavity 12,the spent dialysate in the cavity is pumped out of the patient or cavity12 to a drain 18 or other disposal means. The system 10 then pumps freshdialysate from the supply bags 14 to the patient or peritoneal cavity 12and the procedure is repeated as defined in the therapy protocol. Thesystem 10 in an embodiment pumps a last bag of dialysate (usually, adialysate having a different formulation than the dialysate in the othersupply bags) to the peritoneal cavity 12 for an extended dwell, such asa daytime dwell.

In an embodiment, the system 10 includes a mechanically operateddiaphragm pump 20. The mechanically operated diaphragm pump 20 employs apump motor 22 and a linear pump actuator 24. A vacuum may also be usedwith the mechanical actuator for the diaphragm pump 20, as described infurther detail below. In another embodiment illustrated in FIG. 2, thepump is completely fluidly activated.

In FIG. 1 the system 10 also includes a valve actuator 26, whichmechanically actuates valves V1 to V5. A controller 30 controls thevalve actuator 26 to open valves V1 to V5 as necessary to achieve thedesired direction of dialysate fluid flow. In an embodiment, the valveactuator 26 includes a valve motor 28 and a camshaft (illustratedbelow), which opens one or more of the valves V1 to V5 to achieve thedesired dialysate flow.

The controller 30 includes a plurality of processors and a memory devicefor each processor. The processors include a main microprocessor and anumber of delegate processors. The main microprocessor runs certainhigher level tasks such as the graphical user interface (“GUI”)described below. The delegate processors perform lower level tasks, suchas moving valves, reading sensors, controlling heater duty cycle, etc.An additional processor is provided solely for the purpose of trackingsafety parameters, such as heater plate and medical fluid temperature.For purposes of the present disclosure, except where otherwisespecified, the term “processor 34” refers collectively to all of theprocessors and the term “memory device 32” refers collectively to all ofthe corresponding memory devices.

The controller 30 also includes an input/output (“I/O”) module 36. Thememory device 32 stores a computer program that contains a step by stepsequence for the system 10 and configures certain outputs to occur uponspecified inputs. The processor 34 runs the program in the memory device32. The I/O module 36 accepts signal lines from various sensors. The I/Omodule 36 also connects to power lines including input power lines(including if battery powered) and power lines outputted to the variouselectrical components.

The controller 30, in an embodiment, includes a video controller 38,which may be a video card. The controller 30 also includes a displaydevice or video monitor 40 that displays medical treatment or dialysisinformation to a patient or operator. In an embodiment, the controller30 further includes a touch screen 42 that interfaces with the videomonitor 40 and electrically communicates with the I/O module 36. Thetouch screen 42 enables the patient or operator to input medicaltreatment or dialysis information into the controller 30.

The controller 30 controls the heater 16, the pump 20 and the valveactuator 26 in a number of different phases that make up a singlemedical or dialysis treatment. In a first pump fill phase, controller 30activates the pump 20 to pump medical fluid or dialysate from one of thesupply bags 14. In FIG. 1, the controller 30 commands a vacuum source44, including an air pump motor 46, to pull a vacuum on both sides ofthe pump 20 through a first vacuum line 48 and a second vacuum line 50.The vacuum lines 48 and 50 pull respective vacuums through first andsecond pump chamber walls to suction one of a pair of opposing membranesinside the pump chamber against the interior of the pump chamber. Theother membrane is held against a piston head in the pump 20. The othermembrane alternatively temporarily or permanently mechanically attachesto the piston head, rendering the vacuum on the piston side of the pump20 unnecessary.

With the membranes maintained against the interior of the pump chamberand the piston head, the controller 30 commands the linear actuator 24to withdraw within the pump 20. The withdrawal causes the membranesinside the pump chamber to pull further apart. At this time, thecontroller 30 controls the valve actuator 26 so that only valve V1 isopen. The pulling apart of the membranes causes a negative pressure tooccur in fill line 52, wherein the negative pressure pulls medical fluidor dialysate from the supply bag 14, through the fill line 52, into areceptacle created by the opened membranes inside the pump chamber ofpump 20.

In a patient fill phase, with the negative pressure still maintained bythe vacuum source 44, through the pump chamber walls, on the interiormembranes, the controller 30 causes the linear pump actuator 24 to moveupwards within the pump 20. The upward movement of the actuator 24 andan attached piston head provides a positive mechanical pressure thatcloses the membrane receptacle and thereby pumps the medical fluid outof the pump 20. At this time, the controller 30 controls the valveactuator 26 so that only valves V2 and V3 are open. Consequently, all ofthe fluid exiting pump 20 is pumped through a heater line 54, past thein-line heater 16, through a catheter line 56, and into the patient, forexample, the patient's peritoneal cavity 12. The catheter line 56 in anembodiment connects to a single lumen catheter, which is implanted intothe patient 12. Although, in other embodiments, the system 10 can employa multi-lumen catheter.

The heater 16 in an embodiment includes one or more electrical heatingplates, which heat the medical fluid to roughly body temperature. Thecontroller 30 energizes and de-energizes the heater 16 as necessary toobtain the proper fluid temperature. The controller 30 can close valvesV2 and V3, located on opposing sides of the heater 16 in the heater line54, if the medical fluid is too hot or too cold. The improperly heateddialysate does not enter the peritoneal cavity 12.

The controller 20 repeats the pump fill phase and the heater fill phaseuntil the patient's the peritoneal cavity 12 becomes full of fluidaccording to the therapy protocol. In an embodiment, the volume insidethe pump is about thirty to fifty milliliters, and an adult patienttypically uses about two liters of dialysis fluid. Accordingly, the pumpfill phase and the heater fill phase can be repeated on the order offifty times. In an embodiment, the pump actuator 24 maintains a fluidpressure at the pump 20 of about three pounds per square inch (“psi”).

The system 10 provides a fluid volume sensor 60, which measures theactual volume of medical fluid that has been forced through the pump 20.By summing multiple individual pump volumes, the controller accuratelyknows how much medical fluid or dialysate has been delivered to thepatient 12. The system 10 in an embodiment repeats the pump fill phaseand the heater fill phase until the pump 20 has delivered apredetermined volume of medical fluid. The predetermined volume can beinputted into the controller 30 by a patient or operator via the touchscreen 42.

In a dwell phase, the controller 30 lets the medical fluid or dialysateremain within the patient 12 for an amount of time, which can becontrolled by the controller 30, the patient 12 or an operator. In anembodiment, the controller 30 determines the dwell time, but the patient30 or operator can override the system 10 and command that the system 10remove the medical fluid from the patient 12.

In a second pump fill phase, the medical fluid is removed from thepatient 12. The controller 30 and the actuator 26 open valve V4, whileshutting the remaining valves. With the vacuum source still maintaininga negative pressure on the membranes inside the pump 20, the linearactuator 24 withdraws the pump piston within the chamber of pump 20 andreopens the receptacle between the membranes. The negative pressurecreated by the opening receptacle pulls the medical fluid from thepatient 12, through the catheter line 56 and into the membranereceptacle formed inside the pump 20.

In a drain phase, with the negative pressure still maintained by thevacuum source 44, through the pump chamber walls, on the interiormembranes, the controller 30 causes the linear pump actuator 24 to moveupwardly within the pump 20. The upward movement of the actuator 24causes a positive mechanical pressure to close the membrane receptacleand thereby pump the medical fluid out of the pump 20. At this time, thecontroller 30 controls the valve actuator 26 so that only valve V5 isopen. Consequently, all of the fluid exiting pump 20 is pumped through adrain line 58 and into the drain 18. Drain 18 can be a drain bag or adrain pipe inside a home, a hospital or elsewhere.

One embodiment of the fluid volume sensor 60 is described in more detailbelow in connection with the description of the diaphragm pump 20.Besides the fluid volume sensor 60, the system 10 includes various otherdesired types of sensors.

The system 10 includes temperature sensors 62, such as the sensors T1 toT4, which measure the temperature at relevant places within the system10. In an embodiment, the sensors 62 are non-invasive, however, anyother types of temperature sensors may be employed. As illustrated inFIG. 1, sensors T1 and T2 provide redundant post heater feedback of thefluid temperature to the controller 30. Sensor T3 provides a temperatureof the medical fluid prior to heating. Sensor T4 provides the ambienttemperature.

The system 10 also provides temperature sensors 62 that monitor thetemperature of the heater 16. In an embodiment, the heater 16 is anin-line plate heater. The in-line plate heater 16 can have one or moreheater plates, for example, two heater plates having a disposable unitplaced between same. Separate temperature sensors PT1 and PT2 areprovided to monitor the temperature of each of the plates of the plateheater. The system 10 can thereby control each plate heaterindividually.

The system 10 includes one or more air sensors 64, such as the sensorAS1, placed directly at the throat of the inlet and outlet of the pump20. Another air sensor AS2 monitors air in the medical fluid after itleaves the heater 16 and just before the final shut-off valve V3 leadingto the catheter line 56. The controller 30 monitors the air contentsensed by the air sensors 64 and thereby controls the system 10 toperform any necessary air purge. The system 10 can separate anddischarge the air from the fluid or simply convey the air to the drain18. The system 10 also includes an air vent solenoid 66, which isoperated by the controller 30. The air vent solenoid 66 enables thesystem 10 to relieve the vacuum applied to one or both of the membranesin the pump 20.

The system 10 can accumulate air for various reasons. For example, thevalves V1 to V5 and fluid lines, such as lines 52, 54, 56 and 58 maycontain air prior to priming the system 10. The supply bags 14 may alsointroduce air into the pump 20. The patient 12 can also produce certaingasses, which become entrained in the dialysate and enter the pump 20.Further, if minor leaks exist in the fluid disposable or the connectionsto the supply bag 14, the catheter at the patient 12, or the drain bag,the pump 20 can draw air in through the leaks.

The system 10 provides various fluid pressure sensors 68. Fluid pressuresensors FP1 and FP2 provide a redundant pressure reading of the fluid inthe fill line 52 leading to the pump 60. The fluid pressure sensors 68provide a signal to the controller 30 that indicates the respectivefluid pressure at that location. Based on the signals from the pressuresensors FP1 and FP2, the controller 30 operates the fluid pumps andvalves to obtain and maintain a desired fluid pressure. As stated above,the system 10 maintains the pump pressure, for example, at about threepsi.

The system 10 also provides various valve pressure sensors 70. Valvepressure sensors VP1 to VP5 detect the fluid pressure at the valves V1to V5. The system 10 further provides one or more vacuum pressuresensors 72, for example, at the vacuum source 44, to ensure that aproper vacuum is maintained on the membrane receptacle within the pump20.

In an embodiment, the fluid pressure, valve pressure and vacuum sensors68, 70 and 72, respectively, are non-invasive sensors. That is, thesensors do not physically contact (and possibly contaminate) the medicalfluid or dialysate. Of course, the system 10 can include other flow andpressure devices, such as flow rate sensors, pressure gauges,flowmeters, or pressure regulators in any suitable quantity and at anydesired location.

The system 10 also includes various positioning sensors. In anembodiment, the positioning sensors include a linear encoder 74 thatmonitors the position of the linear pump actuator 24 and a rotaryencoder 76 that monitors the angular position of the valve actuator 26or camshaft. An encoder is one type of positioning feedback device thatcan be employed. Other types of positioning feedback systems includeproximity sensors and magnetic pick-ups that sense a pulse, e.g., a geartooth of a gear attached to the camshaft, and output the pulse to acounter or microprocessor.

The encoders 74 and 76 also typically provide a pulsed output, which issent to the controller 30. The pulsed output tells the controller 30 howmany steps or how far the linear pump actuator 24 or the valve actuator26 is from a home position or home index 78. For example, the homeposition 78 can be the pump fully open or pump fully closed position forthe linear encoder 74 and the zero degree position for the rotaryencoder 76.

In an embodiment, the encoders 74 and 76 are absolute type encoders thatknow the location of the home position 78 even after a power loss. Inanother embodiment, the encoders 74 and 76 are incremental encoders anda battery back-up is provided to the controller so that the system 10can maintain the location of the home position 78 even when no externalpower is applied. Further alternatively, system 10 can be programmed toautomatically move the pump actuator 24 and the valve actuator 26 uponpower-up until a home position is sensed, wherein the system 10 canbegin to run the main sequence.

Referring now to FIG. 2, an alternative system 100 is illustrated. Thesystem 100 includes many of the same components having the samefunctionality (and the same reference numbers) as previously described.These components therefore do not need to be described again except tothe extent that their functioning with the new components of system 100differs. The primary difference between the system 100 and the system 10is that the pump 120 of the system 100 is completely fluidly actuatedand does not use the linear pump actuator 24 of the system 10.

In the pump fill phases, described above, the controller 30 activatesthe pump 120 to pump medical fluid or dialysate from one of the supplybags 14. To do so, the controller 30 commands vacuum source 44 (shownseparately from motor 46 in FIG. 2), including a vacuum pump motor 46,to pull a vacuum on both sides of the pump 120, i.e., on both pumpmembranes, through vacuum lines 148 and 149. The vacuum pump motor 46 inthis embodiment includes a rotary encoder 76 and a home position or homeindex 78. The rotary encoder 76 provides positional feedback of a member150 within the vacuum source 44. The system 100 therefore knows if thevacuum source 44 can provide any additional suction or if the member 150has bottomed out within the vacuum source 44.

To draw in medical fluid, the vacuum line 148 pulls a vacuum throughfirst and second pump chamber walls to the pair of opposing membranesinside the pump chamber. The vacuum pulls the membranes against theinterior of the pump chamber. At this time, the controller 30 controlsthe valve actuator 26 so that only valve V1 is open. The pulling apartof the membranes causes a negative pressure to occur in fill line 52,wherein the negative pressure pulls medical fluid or dialysate from thesupply bag 14, through the fill line 52, into a receptacle created bythe volume between the membranes inside the pump chamber of pump 120.

In an alternative embodiment, the pump 120 maintains a constant vacuumon one of the membranes, wherein the opposing membrane does the pumpingwork. To pump fluid out, the vacuum on one or both membranes isreleased. The membranes, which have been stretched apart, spring back toa closed position. This operation is described in detail below.

The system 100 also includes a slightly different valve manifold thanthe system 10. The system 100 includes one less valve than the system10, wherein the system 100 does not provide an extra valve (V3 in system10) directly after the fluid heater 16. Obviously, those of skill in theart can find many ways to configure the valves and fluid flow lines ofthe systems 10 and 100. Consequently, the configuration of the valvesand fluid flow lines of the systems 10 and 100 as illustrated merelyrepresent practical examples, and the present disclosure is not limitedto same.

II. Hardware Unit and Disposable Unit

Referring now to FIGS. 3A, 3B, 4A and 4B, both systems 10 and 100include a hardware unit 110 and a disposable unit 160. The hardware unit110 in an embodiment is portable and can be transported to and from aperson's home. The hardware unit 110 includes a housing 112 thatincludes a base 114 and a lid 116. In an embodiment, the lid 116 ishinged to the base 114. Alternatively, the lid 116 is completelyremovable from the base. The lid 116 in either case opens to provideaccess to the interior of the housing 112, so as to allow the patient oroperator to place and remove the disposable unit 160 into and from thehardware unit 110. The hardware unit 110 can be made of any protective,hard, resilient and/or flexible material, for example, plastic or metalsheet, and can have a decorative and/or finished surface.

Once the disposable unit 160 is placed inside the hardware unit 110, theoperator closes the lid 116 and uses one or more locking or latchingmechanism 118 (FIG. 3B) to safely house the disposable unit 160 withinthe hardware unit 110. FIG. 4A illustrates members 119 of the housing112 to which the latching mechanism 118 of the lid 116 attaches. Thehardware unit 110 displays the video monitor 40, which can have anassociated touch screen 42 to input commands as described above.Alternatively, or in addition to the touch screen 42, the hardware unit110 can provide one or more electromechanical switches or pushbuttons43, 124, 125 and 127, analog controls 122 and/or lighted displays. Thepushbuttons or switches 43, 124, 125 and 127 and knob 122 enable thepatient or operator to input commands and information into the systems10 and 100. The video monitor 40 provides medical treatment information126 to the patient or operator.

FIG. 3B illustrates one set of dimensions for the hardware unit 110 ofthe present disclosure. The size and weight of the present disclosureare less than previous automated dialysis system. This feature beliesthe portability and ease of use of the system 10, 100 of the presentdisclosure. The size and weight enable the hardware unit 110 to beshipped economically by standard overnight courier services. In theevent that the system 10, 100 of the present disclosure breaks down, areplacement unit can be economically shipped to the patient in time forthe next therapy.

The hardware unit 110 in an embodiment is approximately 23 to 30 cm highand deep and in one embodiment, as illustrated, about 25 cm high anddeep. The hardware unit 110 in an embodiment is approximately 32 to 40cm wide and in one embodiment, as illustrated, about 34 cm wide. Theinternal volume of the unit 110 is therefore about 17,000 cm³ to about36,000 cm³, and in one embodiment, approximately 21,250 cm³ (1310 in³).Section view 4B aptly illustrates the many components maintained withinthis compact space and the efficient use of same. All these componentsand the hardware unit 110 have a total mass of about six to ninekilograms (“kg”) and in one embodiment about seven kilograms.

FIGS. 3A to 4B also illustrate that the architecture, configuration andlayout of the hardware unit 110 provides an automated system that isalso convenient to use. The components of the system 10,100 with whichthe patient must interact are placed on the top, front and sides of theunit 110. The flow control components are placed below the heater 116,which is placed below the disposable unit loading station. The monitor40 and controls 43, 122, 124, 125 and 127 are placed in the front of theunit 110.

The hardware unit 110 contains the pump 20 or 120 and the linear pumpactuator 24 if system 10 is employed. The hardware unit 110 alsocontains the valve actuator 26 including the valve motor 28, the in-lineheater 16, the various sensors, the vacuum source 44 including the airpump motor 46 and the controller 30 as well as the other hardwaredescribed above. FIG. 4B illustrates that one of the pump chamber wallsof the pump 20 or 120 is disposed in the lid 116 of the housing. In FIG.4B, the heater 16 is disposed in the base 114 of the housing 112.Alternatively or additionally, the heater may be placed in the lid 116.The base 114 also contains the opposing pump chamber wall.

Referring now to FIGS. 3A, 4A, 4B, 5 and 6, various embodiments of thedisposable unit 160 are illustrated. In each of the embodiments, thedisposable unit 160 includes a pair of flexible membranes, including anupper flexible membrane 162 and a lower flexible membrane 164. Thedisposable unit 160 of FIG. 6 includes two pairs of flexible membranes,namely, membrane pair 166 and membrane pair 168. Each of the membranepairs 166 and 168 also includes the upper flexible membrane 162 and thelower flexible membrane 164.

The flexible membranes 162 and 164 can be made of any suitable sterileand inert material, such as a sterile and inert plastic or rubber. Forexample, the membranes 162 and 164 can be buna-N, butyl, hypalon, kel-F,kynar, neoprene, nylon, polyethylene, polystyrene, polypropylene,polyvinyl chloride, silicone, vinyl, viton or any combination of these.One material for the flexible membrane is described below in connectionwith FIGS. 13 and 14.

The membranes 162 and 164 are sealed together in various places tocreate fluid flow paths and receptacles between the membranes 162 and164. The seals are heat seals, adhesive seals or a combination of both.FIGS. 3A, 4A, 5 and 6 illustrate that a generally circular seal 170creates a substantially circular fluid pump receptacle 172 between themembranes 162 and 164. The pump receptacle 172 operates with the fluidpumps. Instead of the seal 170, one alternative embodiment is for thebase 114 and lid 116 to press the membranes together to form the seal.FIGS. 4A and 5 illustrate that in an embodiment, the disposable unit 160provides a secondary seal 174 to protect the systems 10 and 100 in casethe primary seal 170 leaks or degrades during use.

FIGS. 3A, 4A and 4B illustrate that the fluid pump receptacle 172 fitsbetween the clamshell shapes of the pumps 20 and 120 in the lid 116. Theclamshell shapes defined by the base 114 and lid 116 of the hardwareunit 110 together with the fluid pump receptacle 172 form the pumpchamber of the pumps 20 and 120 of the present disclosure. The clamshellshapes in the base 114 and lid 116 include one or more ports with whichto draw a vacuum on the membranes 162 and 164. In this manner, themembranes 162 and 164 are pulled towards and conform to the clamshellshapes in the base 114 and lid 116 and thereby create a negativepressure inside the receptacle 172 that pulls medical fluid from asupply bag 14 located outside the hardware unit 110, into the receptacle172.

FIGS. 3A, 4A, 5 and 6 illustrate that a generally rectangular, spiralseal 178 creates a spiral heating path 180 between the membranes 162 and164. The fluid heating path 180 runs from a valve manifold 190, throughthe spiral section, and back to the valve manifold 190. FIG. 4Aillustrates that the fluid heating path 180 fits between the heatingplates of the heater 16, which reside in the base 114 and lid 116 of thehardware unit 110. Providing a heat source on either side of the fluidheating path 180 enables the medical fluid to be quickly and efficientlyheated. In alternative embodiments, however, the heater 16 can includeonly a single heater on one side of the fluid heating path 180 definedby the disposable unit 160 or multiple heaters on each side of thedisposable unit 160.

The upper and lower membranes 162, 164 are attached to the disposableunit 160 utilizing heat sealing techniques as described herein. Themembranes 162 and 164 are expandable so that when the disposable unit160 is placed between a predefined gap between the upper and lowerplates of the heater 16, the membranes 162 and 164 expand and contactthe heater plates. This causes conductive heating to take place betweenthe plates of the heater 16 and the membranes 162, 164 and between themembranes and the medical fluid. The predefined gap is slightly largerthan the thickness of the disposable unit 160. Specifically, whendialysate moves through the fluid heating path 180 of the disposableunit 160, the membranes 162, 164 of the spiral wound fluid heatingpathway 180 expand between the spiral seal 178 and touch the plates ofthe heater 16.

A. Separate Sets of Membranes

The disposable unit 160 of FIG. 6 is similar to the disposable units 160of FIGS. 3A through 5. The in-line fluid heating path 180, however, isplaced in a separate membrane pair 166 from the fluid pump receptacle172 and the valve manifold 190, which are placed in a separate membranepair 168. A pair of flexible tubes 182 and 184, which can be anysuitable medical grade tubing, fluidly connect the valve manifold 190 tothe fluid heating path 180. The tubes 182 and 184 can be connected tothe membrane pairs 166, 168 by any desired means, such as, heat sealing,bonding, press-fitting or by any other permanent or removable fluidconnection. When placed in the hardware unit 110, the heater 16 heatseach side of the heater membrane pair 166, as in the other embodiments.

Separating the fluid heating path 180 from the fluid pump receptacle 172and the valve manifold 190 enables the membranes of the respective pairsto be made of different materials. It is desirable that the membranes162 and 164 of the heating pair 166 conduct or radiate heat efficiently.On the other hand, it is desirable that the membranes 162 and 164 of thefluid flow pair 166 withstand the forces of suction and mechanicalactuation. It may therefore be desirable to use dissimilar materials forthe membrane pair 166 and the membrane pair 168.

The membrane pair 166, defining the heater fluid flow path 180,additionally defines alignment holes 176 that align with pegs protrudingfrom the base 114 or the lid 116 of the hardware unit 110. Each of theembodiments of the disposable unit 160 disclosed herein may be adaptedto include alignment holes 176, which aid the patient or operator inproperly placing the disposable unit 160 within the housing 112 of thehardware unit 110.

B. Rigid Frame and Bowed Sides

As shown in FIGS. 3A, 4A and 5, each of the embodiments of thedisposable unit 160 disclosed herein may also be adapted to provide arigid or semi-rigid member or frame 186, which in an embodiment,surrounds or substantially circumscribes the membranes 162 and 164 ofthe disposable unit 160. In an embodiment, the rigid member or frame 186is made of a sterile, inert, rigid or semi-rigid plastic, for example,from one of or a combination of the plastics listed above for themembranes 162 and 164. The frame 186 aids the patient or operator inproperly placing the disposable unit 160 within the housing 112 of thehardware unit 110.

In an embodiment, the housing 112 defines a pin or guide into which theframe 186 of the disposable unit 160 snugly fits. FIG. 5 illustratesthat the frame 186 defines an aperture 161 that fits onto the pin orguide of the housing 112. The frame 186 can provide a plurality ofapertures, such as the aperture 161, which fit onto a like number ofpins or guides provided by the housing 112. FIG. 5 also illustrates thatthe frame 186 includes an asymmetrical member or chamfer 163. Thechamfer 163 forms an angle, such as forty-five degrees, with respect tothe other sides of the frame 186. The housing 112 defines or provides anarea into which to place the disposable unit 160. The area has theasymmetrical shape of the frame 186 or otherwise provides guides thatonly allow the unit 160 to be placed in the housing 112 from a singledirection. The chamfer 163 and the cooperating housing 112 ensure thatwhen the patient places the disposable unit 160 in the housing 112, thebottom of the disposable unit 160 is placed in the housing 112 and thefluid inlets/outlets 196 face in the proper direction.

As discussed above, the disposable unit 160 includes a valve manifold190. In an embodiment, the valve manifold 190 is made of a rigid orsemi-rigid plastic, such as, from one of or a combination of theplastics listed above for the membranes 162 and 164. The valve manifold190 is covered on either side by the upper and lower membranes 162 and164 to thereby create a sealed and inert logic flow path for the systems10 and 100.

In FIG. 5, the manifold 190 defines holes 192 and slots 194. The holes192 define the location of the valves, for example, valves V1 to V5 ofthe system 10. The slots 194 define the fluid flow paths from the valvesto the fluid pump receptacle 172, the fluid heating path 180 or to fluidinlets/outlets 196. The fluid inlets/outlets 196 individually lead tothe supply bag 14, the catheter line 56, the patient 12 and the drain18. The fluid inlets/outlets 196 may have various configurations andorientations, as contrasted by FIG. 3A. The drain 196 may also beadapted to connect to an external flexible tube via a method known tothose of skill in the art.

In an embodiment, the rigid or semi-rigid frame 186 includes bowed sides187 and 189, as illustrated in FIG. 5. The bowed sides 187 and 189 areformed with the frame 186 before the membranes 162 and 164 heat seal oradhesively seal to the frame 186 and manifold 190. The frame 186 andbowed sides 187 and 189 can be extruded plastic or plastic injectionmolded. The frame 186 can include as little as one bowed side, anynumber less than all, or have all sides be bowed.

In the illustrated embodiment, the sides 187 and 189 bow outwardalthough they can alternatively bow inward. In an embodiment, the sidesare bowed in a direction of the plane of the frame 186 of the disposableunit 160. The bowed sides 187 and 189 increase the rigidity of the frame186 and the disposable unit 160. The disposable unit is accordingly moreeasily placed in the housing 112 of the hardware unit 110. The bowedsides 187 and 189 reduce the amount of flexing or distortion of theframe 186 due to heat sealing or mechanically pressing membranes 162 and164 onto the frame 186 and manifold 190.

C. Heat Seal Interface

Referring now to FIG. 7, an embodiment for heat sealing the membranes162 and 164 to the manifold 190 is illustrated. In an embodiment, themanifold 190 is made of a rigid or semi-rigid plastic material asdescribed above. Heat sealing the membranes 162 and 164 to thesemi-rigid manifold 190, which in an embodiment is an injection moldedcomponent, requires different processing parameters than heat sealingthe individual membranes 162 and 164 together, for example, at seal 170of the fluid pump receptacle 172. In particular, heat sealing themembranes 162 and 164 to the manifold 190 can require more heat, morepressure and more heating time. The semi-rigid or rigid manifold 190 isappreciably thicker than the individual membranes 162 and 164.Consequently, relative to the thin membranes, the thicker manifold 190acts as a heat sink. The bond between the thin membrane and thickermanifold 190 therefore requires more heat or energy than the heat sealbond between the thin membranes 162 and 164.

As illustrated in FIGS. 3A, 4A, 5 and 6, the disposable unit 160requires both membrane to manifold and membrane to membrane seals. It isdesirable to heat seal the entire disposable unit 160 in one step orprocess for obvious reasons. It should also be obvious that the heatsealing process should be performed so as avoid burning or melting oneof the thin membranes 162 or 164.

FIG. 7 illustrates one embodiment for solving the heat sinking disparitybetween varying materials. FIG. 7 illustrates a portion of the manifold190, which is shown in its entirety in FIG. 5. In FIG. 5, the manifold190 illustrates a port that connects to the fluid pump receptacle 172.This port is illustrated as port 205 in FIG. 7. FIG. 5 also illustratestwo ports extending from the manifold 190 that fluidly connect to thefluid heating path 180. These ports are illustrated as ports 201 and 203in FIG. 7. Both FIG. 5 and FIG. 7 illustrate that the injection moldedmanifold 190 defines a plurality of holes 192 and slots 194. The holes192 operate with the valve actuator and the slots 194 to form fluidpathways when enclosed by the membranes 162 and 164.

To reduce the amount of heat necessary to seal the membranes 162 and 164to the manifold 190, the manifold 190 includes a side 193 having alesser thickness than the remaining portion of the manifold 190. Thethinner side 193 has less mass and therefore absorbs less localized heatthan would a manifold of constant thickness. The side 193 also definesor includes a tapered portion 195. The tapered portion 195 provides flatsurfaces on which to seal the membranes 162 and 164 and also positionsthe membranes 162 and 164 together so that in an embodiment a membraneto membrane seal may also be made in addition to the membrane tomanifold 190 seal.

The tapered edges 195 form an interface for the membranes 162 and 164 toseal to the manifold 190, which occurs along continuous stretches of thesides 193 of the manifold 190 that require sealing or that wouldotherwise come into contact with the medical fluid. Therefore, asillustrated in FIG. 5, the side of the manifold 190 defining theinput/output ports 196 does not need to be tapered as illustrated inFIG. 7. Also, as illustrated in FIG. 7, the tapered edges 195 of thethin sides 193 discontinue where the ports 201, 203, and 205 extend fromthe manifold 190.

The ports 201, 203 and 205 also form tapered edges 207. Tapered edges207 form an interface for heat sealing the parts to the membranes 162and 164. As described above, the tapered edges 207 of the ports 201, 203and 205 also enable a membrane to membrane seal to take place directlynext to the membrane to tapered edge 207 seal. The tapered edges 195 and207 in an embodiment gradually taper towards the knife-like edge. Inother embodiments, the tapered edges 195 and 207 may take on differentforms or shapes, such as a rounded edge, a blunter edge or may simply befurther reduced in thickness from side 193 of the manifold 190. Asillustrated, the ports 201, 203 and 205 in an embodiment form ovularopenings. The tapered ovular openings provide a smoother transitionangle than would a circular outer diameter. The ovular openings performas well as round openings from a fluid flow standpoint as long as openarea of the inner oval is not less than the open area of a suitablecircular port.

The ports 201, 203 and 205 also form raised portions 209. The raisedportions 209 form a bead of polymeric material along the tops of theports 201, 203 and 205 and the tapered edges 207. The beads can beadditionally or alternatively placed along the tapered edges 195 and orthe sides 193. The raised portions or beads 209 provide an extra thinarea of plastic that melts or deforms to provide a flux-like sealantthat enables the membranes 162 and 164 to seal to the manifold 190. Thebeads create a concentrated strip of higher temperature plastic than thesurrounding plastic of the manifold 190. The membranes 162 and 164 sealto the manifold 190 without having to heat a larger area of the manifold190. The raised portions or beads 209 help to seal curved portions andcorners created by the manifold 190.

D. One-Piece Tip Protector Organizer and Vented Tip Protector

Referring now to FIG. 8, one embodiment of a one-piece tip protectororganizer 270 is illustrated. In the HOMECHOICE® peritoneal dialysissystem provided by the assignee of the present disclosure, a disposableset is prepackaged and provided to the patient. The patient opens up thepackage, wherein each of the components is sterilized and maintainedwithin the disposable set. The disposable set includes a disposable unitand a number of tubes emanating from the disposable unit. Like thepresent disclosure, the HOMECHOICE® disposable unit includes a drainline tube that connects to one or more fill bag tubes, and a tube thatconnects to a patient transfer set. Each of these tubes requires aseparate tip protector. That is, after sterilizing the inside of thedisposable unit and the tubes, for example, using ethylene oxide, theends of the tubes have to be capped off so that the sterilization of theinside of the system is maintained. The HOMECHOICE® system provides aseparate tip protector for each tube.

The one-piece tip protector organizer 270 of the present disclosureprovides a single body 272 (which may actually be made of a plurality ofpieces) that defines or provides a plurality of tip protectors 274, 276,278 and 280. The vented tip protector 270 not only houses and protectsthe connectors at the ends of the tubes emanating from the disposableunit 160, the one-piece tip protector 270 also organizes and orders thetubes according to the steps of the dialysis therapy. In the illustratedembodiment, the tip protector 274 is a tip protector for a drain lineconnector 284 connected to a drain line 285 that leads to theappropriate port of the disposable unit 160. The tip protectors 276 and278 are supply bag protectors that protect the connectors 286 and 288that connect to the ends of the tubes 287 and 289 that run to a “Y”connection 287/289, wherein the leg of the “Y” connection 287/289 runsto the appropriate port of the disposable unit 160. The tip protector280 is a patient fluid line protector. The tip protector 280 houses andprotects a connector 290 that connects to patient tube 292, which runsto the appropriate port of the disposable unit 160.

Each of the tubes 285, the “Y” connection 287 and 289 and the patientfluid tube 292 in an embodiment are made of polyvinylchloride (“PVC”)having an inner diameter of 4 mm and an outer diameter of 5 mm. Asillustrated, the one-piece tip protector organizer 270 is adaptable toreceive and protect various types of fluid connectors. The fluidconnector 284 that runs via tube 285 to the drain line port of thedisposable unit 160 is in an embodiment largely the same as the portthat emanates from the supply bags 14. The ports that emanate from thesupply bags 14 also include a membrane that is pierced by the sharp stemof the supply bag connectors 286 and 288. The drain line connector 284does not include the membrane of the supply bag 14 as it is not needed.The tip protector 290 that connects to the end of the patient fluid tube292 is discussed in detail below.

In one embodiment, the system 10, 100 of the present disclosure providestwo, six liter supply bags 14. The two, six liter bags provide aneconomic amount of peritoneal dialysis fluid, which is enough fluid toprovide a number of fill, dwell and drain cycles during the eveningwhile the patient sleeps. The one-piece organizer 270 therefore providestwo tip protectors 276 and 278, which house and protect the supplyconnectors 286 and 288. In alternative embodiments, the one-pieceorganizer 270 can define or provide any number of supply bag tipprotectors. Any number of supply bags can be additionally linked via “Y”or “T” type tubing links.

The one-piece organizer 270 can provide additional tip protectors suchas a last bag protector, which protects a line that runs to a bag thatholds enough peritoneal fluid, e.g., two liters, for a final fill forthe patient during the daytime. In this case, an additional last bagtube, not illustrated, would connect to a connector, which would be abag piercing connector, the same as or similar to the fill bagconnectors 286 and 288.

The body 272 of the tip protector organizer 270 is in an embodiment alsomade of PVC. The tip protectors 274, 276, 278 and 280 are injectionmolded or blow molded. Alternatively, the tip protectors can beseparately applied to the body 272. As seen in FIG. 8, one or more ofthe tip protectors can include flutes, threads or other protrusions thataid in grasping and holding the respective tube connector. Further,while the organizer 270 is generally referred to herein as a “one-piece”organizer, the organizer 270 may itself be comprised of any number orpieces. “One-piece” refers to the feature that a single unit houses amultitude or tip protectors.

The one-piece organizer 270 also includes a rim 294 that extendsoutwardly from the main portion of the body 272, and which circumventsthe main portion of the body 272. Referring now to FIG. 9, a crosssection of the one-piece organizer 270 illustrates that the rim 294tapers downwardly from the drain line tip protector 274 towards thepatient fluid tip protector 280. That is, the rim 294 is higher orthicker at the drain line end than it is at the patient fluid line end.This enables the one-piece tip protector organizer 270 to be mounted tothe hardware unit 110 in only one orientation.

FIG. 3A illustrates that the one-piece tip protector organizer 270 in anembodiment slides into the hardware unit 110 vertically. The hardwareunit 110 includes or provides a pair of members 296 that extendoutwardly from a side wall of the hardware unit 110. FIGS. 3B and 4Aillustrate another embodiment, wherein the rim 294 of the organizer 270slides vertically into a notch 297 defined or provided by the base 114of the housing 112 of the hardware unit 110. The rim 294 of theorganizer 270 slides between the members 296 and the side wall of thehardware unit 110. The members 296 extend further outwardly as theyextend running towards the top of the hardware unit 110. The taper ofthe members 296 corresponds to the taper of the rim 294 of the organizer270 so that the organizer 270 can only slide into the hardware unit 110vertically from one direction.

FIG. 9 also illustrates that the tip protectors 274, 276, 278 and 280can have various cross-sectional shapes. Each of the tip protectorsincludes a solid bottom and sides that seal around the respectiveconnectors 284, 286, 288 and 290, so that the one-piece organizer 270maintains the sterility of the system even after the patient removes thedisposable set from a sealed sterilized container. The one-pieceorganizer 270 illustrated in FIGS. 8 and 9 mounts in a sturdy fashion tothe side of the hardware unit 110. Via this solid connection, thepatient is able to remove the tubes 285, 287, 289 and 292 using only onehand in many cases. The interface between the hardware unit 110 and theorganizer 270 simplifies the procedure for the patient and provides asolid, sterile environment for the tubes and associated connectors untilused.

FIG. 3A also illustrates another possible embodiment wherein analternative one-piece organizer 298 is integral to or provided by theframe 186 of the disposable unit 160. Here, the tubes 196, indicatedgenerally, are horizontally organized as opposed to the verticalarrangement of the tip protector 270 in the housing 112. The horizontalone-piece organizer 298 illustrates that the concept of protecting andorganizing the tubes before use can be provided in a variety of placesand orientations in the system 10.

In one embodiment, the tip protector and organizer 270 structures thetubes 285, 287, 289 and 292 in a downwardly vertical order, such thatthe first tube that the patient is supposed to pull when starting thedialysis therapy is provided on top, the next tubes that the patient issupposed to pull are provided in the middle and the final tube isprovided lowest on the vertically oriented one-piece organizer 270.According to one protocol, the patient first removes the drain connector284 from the tip protector 274 and runs the drain line 285 to a toilet,drain bag or other drain. The patient then removes the supply connectors286 and 288 and punctures the supply bags 14 (FIGS. 1 and 2). At thispoint, dialysate can be pumped to the disposable unit 160 and throughoutthe system 10. The controller 30 of the system 10, 100 begins a primingcycle, which is discussed in more detail below.

Once priming is complete, system 10, 100 prompts the patient to removethe primed patient line 292 and connect same to the transfer setimplanted into the patient. The transfer set (not illustrated) includesa catheter positioned into the patient's peritoneal cavity and a tuberunning to the catheter. The tube also includes a connector that couplesto the connector 290. At this point, system 10, 100 can begin to eitherdrain spent peritoneal fluid from the patient 12 to the drain 18 or pullnew fluid from one or both of the supply bags 14 and fill the patient'speritoneal cavity 12.

Referring now to FIGS. 10 to 12, one embodiment for the patient line tipprotector 280 of the present disclosure is illustrated. The HOMECHOICE®system produced by the assignee of the present disclosure primes thepatient fluid line by allowing the patient connector to be heldvertically approximately at the same level as the supply bag. In thismanner, when the HOMECHOICE® system primes the disposable unit, gravityfeeds peritoneal fluid into the patient fluid line up to the end of thepatient fluid connector. The patient fluid connector is open so that aircan freely escape when the peritoneal fluid is fed by gravity throughthe patient line. HOMECHOICE® system enables the patient fluid line tobe primed without counting pump strokes or having to meter out a knownvolume of dialysate, techniques which are complicated and prone tofailure.

The system 10, 100 of the present disclosure provides a differentapparatus and method of priming without having to calculate the amountof fluid that is needed to just reach but not surpass the patientconnector of the patient fluid line. FIG. 10 shows a cross-section ofthe patient fluid connector 290 that has been inserted into the ventedtip protector 280. FIG. 11 illustrates a cross section of the patientfluid connector 290 only. FIG. 12 illustrates a cross section of the tipprotector 280 only. A hydrophobic membrane 300 is placed on the outeredge of the tip protector 280. The tip protector 280 defines a fluidlumen 302 that runs through the entire length of the tip protector 280.The hydrophobic membrane 300 covers the fluid lumen 302. The hydrophobicmembrane 300 allows air to purge from inside the patient's fluid linebut does not allow water or peritoneal fluid to flow through same.

It should be appreciated that the vented tip protector 280 including thehydrophobic membrane 300 is not limited to being placed in the one-piecetip protector organizer 270. FIG. 9 illustrates that the one-pieceorganizer 270 does include the patient tip protector 280 having thehydrophobic membrane 300 and the fluid lumen 302. The vented tipprotector 280 in an alternative embodiment, however, can be provided asa separate or stand alone tip protector, similar to the one used on theHOMECHOICE® system provided by the assignee of the present disclosure.

Hydrophobic membranes, such as the hydrophobic membrane 300 employedherein, are commercially available. One suitable hydrophobic membrane isproduced by Millipore, 80 Ashby Road, Bedford, Mass. 01730. FIG. 12 bestillustrates that the hydrophobic membrane heat seals or sonically sealsto the tip protector 280. The fluid lumen 302 in an embodiment isrelatively small in diameter, such as approximately fifty to seventythousandths of an inch (1.25 to 1.75 mm).

The vented tip protector 280 and the patient fluid connector 290 alsocooperate so that when the system 10, 100 is completely primed, the tipprotector 280 and connector 290 minimize the amount of fluid that spillswhen the patient removes the patient fluid connector 290 from the tipprotector 280. The connector 290 includes or provides a male lure 304that mates with a female lure 306 best seen in FIG. 10. The mating lures304 and 306 prevent peritoneal fluid from filling the cavity of the tipprotector 280, which must be wide enough to house the flange 308 of thepatient fluid connector 290. FIG. 12 illustrates that the seal interfacebetween the male lure 304 of the connector 290 and the female lure 306of the vented tip protector 280 reduces the volume significantly from aninterior volume 310 existing around the male lure 304 to the fifty toseventy thousandths diameter of the lumen 302.

To prime the system 10, 100 the patient removes the drain line 285 fromthe tip protector 274 and places it into a tub, toilet or drain bag 18.The patient removes the two or more supply bag connectors 286 and 288and punctures seal membranes (not illustrated) of the supply bags 14.System 10, 100 may then automatically begin pump priming or may beginpump priming upon a patient input. In either case, system 10, 100 pumpsfluid from one or both of the supply bags 14 through the connectors 286and 288 and tubes 287 and 289, into the disposal disposable unit 160,out the patient fluid line 292 and into the patient fluid connector 290,which is still housed in the vented tip protector 280 of the one-pieceorganizer 270. The organizer 270 is vertically housed in the hardwareunit 110 as seen in FIGS. 3A and 3B.

When the peritoneal fluid reaches the patient fluid connector 290, mostall the air within the system 10 has been pushed through the hydrophobicmembrane 300 attached at the end of the tip protector 280 housed in theone-piece tip protector 270. The nature of the hydrophobic membrane 300is that it allows air to pass through but filters or does not allowwater or peritoneal fluid to pass through same. Thus, when the fluidfinally reaches the hydrophobic membrane 300, the lack of any additionalspace in which to flow fluid causes the pressure to increase within thesystem 10, 100. The system 10, 100 provides one or more pressuresensors, for example pressure sensors 68 (marked as FP1, FP2 and FPT inFIGS. 1 and 2).

One or more of the pressure sensors 68 sense the increase in pressuredue to the peritoneal fluid backing up against the hydrophobic filter300. The pressure sensor(s) sends a signal to the I/O module 36 of thecontroller 30. The controller 30 receives the signal and is programmedin memory device 32 to shut down the diaphragm pump 20, 120. In thismanner, the system 10 self-primes each of the fill lines 287 and 289,the disposable unit 160 and the patient fluid line 292 automatically andwithout need for controlled volume calculations or gravity feeding.

System 10, 100 also includes one or more safety features that may bebased upon a volume calculation. That is, under normal operations, thesystem 10, 100 does not control the priming using a volume calculation.However, in the case where for example the patient removes the patientfluid connector 290 from the vented tip protector 280 of the one-piecetip organizer 270 before the system 10, 100 senses a pressure increaseand stops the pumps 10, 100, the system 10, 100 can employ an alarmcalculation, wherein the system 10, 100 knows that it has pumped toomuch peritoneal fluid (e.g., a predetermined amount more than theinternal volume of the system) and shuts down pump 20, 120 accordingly.

III. Membrane Material for the Disposable Unit

Referring now to FIGS. 13 and 14, upper and lower membranes 162, 164 canbe fabricated from a monolayer film structure 312 (FIG. 13) or amultiple layer film structure 312 (FIG. 14). The film 312 is constructedfrom a non-PVC containing polymeric material and must satisfy numerousphysical property requirements. The film 312 must have a low modulus ofelasticity so that it can be deformed under low pressure to function asa pumping element. What is meant by low modulus is the film 312 has amodulus of elasticity when measured in accordance with ASTM D882, ofless than about 10,000 psi, more preferably less than about 8,000 psiand even more preferably less than about 5,000 psi and finally, lessthan about 3,000 psi, or any range or combination of ranges defined bythese numbers. The film 312 must have adequate thermal conductivity toallow for in-line heating. The film has a thermal conductivity ofgreater than 0.13 W/meters-° K when measured using a Hot Disk™ sold byMathis Instruments Ltd. The film 312 must be capable of being heatsealed to cassette 160. The film 312 must be capable of being sterilizedby exposure to gamma rays, by exposure to steam for a period of time(typically 1 hour), and exposure to ethylene oxide without significantdegradation of the film or having an adverse effect on the dialysissolution. Finally, the film 312 must be capable of being extruded athigh rates of speed of greater than 50 ft/min.

The monolayer structure 312 is formed from a blend of from about 90% toabout 99% by weight of a first component containing a styrene andhydrocarbon copolymer and from about 10% to about 1% of a melt strengthenhancing polymer and more preferably a high melt strengthpolypropylene.

The term “styrene” includes styrene and the various substituted styrenesincluding alkyl substituted styrene and halogen substituted styrene. Thealkyl group can contain from 1 to about 6 carbon atoms. Specificexamples of substituted styrenes include alpha-methylstyrene,beta-methylstyrene, vinyltoluene, 3-methylstyrene, 4-methylstyrene,4-isopropylstyrene, 2,4-dimethylstyrene, o-chloro styrene, p-chlorostyrene, o-bromostyrene, 2-chloro-4-methylstyrene, etc. Styrene is themost preferred.

The hydrocarbon portion of the styrene and hydrocarbon copolymerincludes conjugated dienes. Conjugated dienes which may be utilized arethose containing from 4 to about 10 carbon atoms and more specifically,from 4 to 6 carbon atoms. Examples include 1,3-butadiene,2-methyl-1,3-butadiene (isoprene), 2,3-dimethyl-1,3-butadiene,chloroprene, 1,3-pentadiene, 1,3-hexadiene, etc. Mixtures of theseconjugated dienes also may be used such as mixtures of butadiene andisoprene. The preferred conjugated dienes are isoprene and1,3-butadiene.

The styrene and hydrocarbon copolymers can be block copolymers includingdi-block, tri-block, multiblock, and star block. Specific examples ofdiblock copolymers include styrene-butadiene, styrene-isoprene, andselectively hydrogenated derivatives thereof. Examples of tri-blockpolymers include styrene-butadiene-styrene, styrene-isoprene-styrene,alpha-methylstyrene-butadiene-alpha-methylstyrene, andalpha-methylstyrene-isoprene-alpha-methylstyrene and selectivelyhydrogenated derivatives thereof.

The selective hydrogenation of the above block copolymers may be carriedout by a variety of well known processes including hydrogenation in thepresence of such catalysts as Raney nickel, noble metals such asplatinum, palladium, etc., and soluble transition metal catalysts.Suitable hydrogenation processes which can be used are those wherein thediene-containing polymer or copolymer is dissolved in an inerthydrocarbon diluent such as cyclohexane and hydrogenated by reactionwith hydrogen in the presence of a soluble hydrogenation catalyst. Suchprocedures are described in U.S. Pat. Nos. 3,113,986 and 4,226,952, thedisclosures of which are incorporated herein by reference and made apart hereof.

Particularly useful hydrogenated block copolymers are the hydrogenatedblock copolymers of styrene-isoprene-styrene, such as apolystyrene-(ethylene/propylene)-polystyrene block polymer. When apolystyrene-polybutadiene-polystyrene block copolymer is hydrogenated,the resulting product resembles a regular copolymer block of ethyleneand 1-butene (EB). This hydrogenated block copolymer is often referredto as SEBS. When the conjugated diene employed is isoprene, theresulting hydrogenated product resembles a regular copolymer block ofethylene and propylene (EP). This hydrogenated block copolymer is oftenreferred to as SEPS. When the conjugated diene is a mixture of isopreneand butadiene the selectively hydrogenated product is referred to asSEEPS. Suitable SEBS, SEPS and SEEPS copolymers are sold by Shell Oilunder the tradename KRATON, by Kurary under the tradename SEPTON® andHYBRAR®.

The block copolymers of the conjugated diene and the vinyl aromaticcompound can be grafted with an alpha,beta-unsaturated monocarboxylic ordicarboxylic acid reagent. The carboxylic acid reagents includecarboxylic acids per se and their functional derivatives such asanhydrides, imides, metal salts, esters, etc., which are capable ofbeing grafted onto the selectively hydrogenated block copolymer. Thegrafted polymer will usually contain from about 0.1 to about 20%, andpreferably from about 0.1 to about 10% by weight based on the totalweight of the block copolymer and the carboxylic acid reagent of thegrafted carboxylic acid. Specific examples of useful monobasiccarboxylic acids include acrylic acid, methacrylic acid, cinnamic acid,crotonic acid, acrylic anhydride, sodium acrylate, calcium acrylate andmagnesium acrylate, etc. Examples of dicarboxylic acids and usefulderivatives thereof include maleic acid, maleic anhydride, fumaric acid,mesaconic acid, itaconic acid, citraconic acid, itaconic anhydride,citraconic anhydride, monomethyl maleate, monosodium maleate, etc.

The first component containing a styrene and hydrocarbon block copolymercan be modified by adding an oil, such as a mineral oil, paraffinic oil,polybutene oil or the like. The amount of oil added to the styrene andhydrocarbon block copolymer is from about 5% to about 40%. The firstcomponent can also contain a polypropylene up to about 20% by weight ofthe first component. One particularly suitable first component is an oilmodified SEBS sold by the Shell Chemical Company under the productdesignation KRATON G2705.

The melt strength enhancing polymer preferably is a high melt strengthpolypropylene. Suitable high melt strength polypropylenes can be ahomopolymer or a copolymer of polypropylene and can have free end longchain branching or not. In one preferred form of the invention, the highmelt strength polypropylene will have a melt flow index within the rangeof 10 grams/10 min. to 800 grams/10 min., more preferably 10 grams/10min. to 200 grams/10 min, or any range or combination of ranges therein.High melt strength polypropylenes are known to have free-end long chainbranches of propylene units. Methods of preparing polypropylenes whichexhibit a high melt strength characteristic have been described in U.S.Pat. Nos. 4,916,198; 5,047,485; and 5,605,936, which are incorporatedherein by reference and made a part hereof. One such method includesirradiating a linear propylene polymer in an environment in which theactive oxygen concentration is about 15% by volume with high energyionization radiation at a dose of 1×10⁴ megarads per minute for a periodof time sufficient for a substantial amount of chain scission of thelinear propylene polymer to occur but insufficient to cause the materialto become gelatinous. The irradiation results in chain scission. Thesubsequent recombination of chain fragments results in the formation ofnew chains, as well as joining chain fragments to chains to formbranches. This further results in the desired free-end long chainbranched, high molecular weight, non-linear, propylene polymer material.Radiation is maintained until a significant amount of long chainbranches form. The material is then treated to deactivate substantiallyall the free radicals present in the irradiated material.

High melt strength polypropylenes can also be obtained as described inU.S. Pat. No. 5,416,169, which is incorporated in its entirety herein byreference and made a part hereof, when a specified organic peroxide(di-2-ethylhexyl peroxydicarbonate) is reacted with a polypropyleneunder specified conditions, followed by melt-kneading. Suchpolypropylenes are linear, crystalline polypropylenes having a branchingcoefficient of substantially 1, and, therefore, has no free endelong-chain branching and will have a intrinsic viscosity of from about2.5 dl/g to 10 dl/g.

Suitable copolymers of propylene are obtained by polymerizing apropylene monomer with an α-olefin having from 2 to 20 carbons. In amore preferred form of the invention the propylene is copolymerized withethylene in an amount by weight from about 1% to about 20%, morepreferably from about 1% to about 10% and most preferably from 2% toabout 5% by weight of the copolymer. The propylene and ethylenecopolymers may be random or block copolymers. In a preferred form of theinvention, the propylene copolymer is obtained using a single-sitecatalyst.

The components of the blend can be blended and extruded using standardtechniques well known in the art. The film 312 will have a thickness offrom about 3 mils to about 12 mils, more preferably from 5 mils to about9 mils.

FIG. 14 shows a multiple layer film having a first layer 314 and asecond layer 316. FIG. 14 shows the use of two layers but the presentdisclosure contemplates using more than two layers provided theabove-mentioned material property requirements are met. The first layer314 can be of the same polymer blend used to fabricate the monolayerstructure and in a more preferred form of the invention will define aseal layer for joining the film the cassette 160. The second layer 316can be made from non-PVC containing materials and preferably is selectedfrom polyolefins, polybutadienes, polyesters, polyester ethers,polyester elastomers, polyamides and the like and blends of the same. Atie layer or tie layers (not shown) may be required to adhere additionallayers to the first layer 314.

Suitable polyolefins include homopolymers and copolymers obtained bypolymerizing alpha-olefins containing from 2 to 20 carbon atoms, andmore preferably from 2 to 10 carbons. Therefore, suitable polyolefinsinclude polymers and copolymers of propylene, ethylene, butene-1,pentene-1,4-methyl-1-pentene, hexene-1, heptene-1, octene-1, nonene-1and decene-1. Most preferably the polyolefin is a homopolymer orcopolymer of propylene or a homopolymer or copolymer of polyethylene.

Suitable homopolymers of polypropylene can have a stereochemistry ofamorphous, isotactic, syndiotactic, atactic, hemiisotactic orstereoblock. In one preferred form of the invention the homopolymer ofpolypropylene is obtained using a single site catalyst.

It is also possible to use a blend of polypropylene and α-olefincopolymers wherein the propylene copolymers can vary by the number ofcarbons in the α-olefin. For example, the present disclosurecontemplates blends of propylene and α-olefin copolymers wherein onecopolymer has a 2 carbon α-olefin and another copolymer has a 4 carbonα-olefin. It is also possible to use any combination of α-olefins from 2to 20 carbons and more preferably from 2 to 8 carbons. Accordingly, thepresent disclosure contemplates blends of propylene and α-olefincopolymers wherein a first and second α-olefins have the followingcombination of carbon numbers: 2 and 6, 2 and 8, 4 and 6, 4 and 8. It isalso contemplated using more than 2 polypropylene and α-olefincopolymers in the blend. Suitable polymers can be obtained using acatalloy procedure.

It may also be desirable to use a high melt strength polypropylene asdefined above.

Suitable homopolymers of ethylene include those having a density ofgreater than 0.915 g/cc and includes low density polyethylene (LDPE),medium density polyethylene (MDPE) and high density polyethylene (HDPE).

Suitable copolymers of ethylene are obtained by polymerizing ethylenemonomers with an α-olefin having from 3 to 20 carbons, more preferably3-10 carbons and most preferably from 4 to 8 carbons. It is alsodesirable for the copolymers of ethylene to have a density as measuredby ASTM D-792 of less than about 0.915 g/cc and more preferably lessthan about 0.910 g/cc and even more preferably less than about 0.900g/cc. Such polymers are oftentimes referred to as VLDPE (very lowdensity polyethylene) or ULDPE (ultra low density polyethylene).Preferably the ethylene α-olefin copolymers are produced using a singlesite catalyst and even more preferably a metallocene catalyst systems.Single site catalysts are believed to have a single, sterically andelectronically equivalent catalyst position as opposed to theZiegler-Natta type catalysts which are known to have a mixture ofcatalysts sites. Such single-site catalyzed ethylene α-olefins are soldby Dow under the trade name AFFINITY, DuPont Dow under the trademarkENGAGE® and by Exxon under the trade name EXACT. These copolymers shallsometimes be referred to herein as m-ULDPE.

Suitable copolymers of ethylene also include ethylene and lower alkylacrylate copolymers, ethylene and lower alkyl substituted alkyl acrylatecopolymers and ethylene vinyl acetate copolymers having a vinyl acetatecontent of from about 5% to about 40% by weight of the copolymer. Theterm “lower alkyl acrylates” refers to comonomers having the formula setforth in Diagram 1:

The R group refers to alkyls having from 1 to 17 carbons. Thus, the term“lower alkyl acrylates” includes but is not limited to methyl acrylate,ethyl acrylate, butyl acrylate and the like.

The term “alkyl substituted alkyl acrylates” refers to comonomers havingthe formula set forth in Diagram 2:

R₁ and R₂ are alkyls having 1-17 carbons and can have the same number ofcarbons or have a different number of carbons. Thus, the term “alkylsubstituted alkyl acrylates” includes but is not limited to methylmethacrylate, ethyl methacrylate, methyl ethacrylate, ethyl ethacrylate,butyl methacrylate, butyl ethacrylate and the like.

Suitable polybutadienes include the 1,2- and 1,4-addition products of1,3-butadiene (these shall collectively be referred to aspolybutadienes). In a more preferred form of the invention the polymeris a 1,2-addition product of 1,3 butadiene (these shall be referred toas 1,2 polybutadienes). In an even more preferred form of the inventionthe polymer of interest is a syndiotactic 1,2-polybutadiene and evenmore preferably a low crystallinity, syndiotactic 1,2 polybutadiene. Ina preferred form of the invention the low crystallinity, syndiotactic1,2 polybutadiene will have a crystallinity less than 50%, morepreferably less than about 45%, even more preferably less than about40%, even more preferably the crystallinity will be from about 13% toabout 40%, and most preferably from about 15% to about 30%. In apreferred form of the invention the low crystallinity, syndiotactic 1,2polybutadiene will have a melting point temperature measured inaccordance with ASTM D 3418 from about 70° C. to about 120° C. Suitableresins include those sold by JSR (Japan Synthetic Rubber) under thegrade designations: JSR RB 810, JSR RB 820, and JSR RB 830.

Suitable polyesters include polycondensation products of di- orpolycarboxylic acids and di or poly hydroxy alcohols or alkylene oxides.In a preferred form of the invention the polyester is a polyester ether.Suitable polyester ethers are obtained from reacting 1,4 cyclohexanedimethanol, 1,4 cyclohexane dicarboxylic acid and polytetramethyleneglycol ether and shall be referred to generally as PCCE. Suitable PCCE'sare sold by Eastman under the trade name ECDEL. Suitable polyestersfurther include polyester elastomers which are block copolymers of ahard crystalline segment of polybutylene terephthalate and a secondsegment of a soft (amorphous) polyether glycols. Such polyesterelastomers are sold by Du Pont Chemical Company under the trade nameHYTREL®.

Suitable polyamides include those that result from a ring-openingreaction of lactams having from 4-12 carbons. This group of polyamidestherefore includes nylon 6, nylon 10 and nylon 12. Acceptable polyamidesalso include aliphatic polyamides resulting from the condensationreaction of di-amines having a carbon number within a range of 2-13,aliphatic polyamides resulting from a condensation reaction of di-acidshaving a carbon number within a range of 2-13, polyamides resulting fromthe condensation reaction of dimer fatty acids, and amide containingcopolymers. Thus, suitable aliphatic polyamides include, for example,nylon 66, nylon 6,10 and dimer fatty acid polyamides.

In a preferred from of the invention, the cassette 160 is fabricatedfrom a material that is adhesively compatible with the upper and lowermembrane 162, 164. What is meant by adhesive compatibility is themembrane can be attached to the cassette using standard heat sealingtechniques. One particularly suitable material is a polymer blend of apolyolefin and a styrene and hydrocarbon copolymer. More particularly,the polyolefin of the polymer blend is a polypropylene and even morepreferably a polypropylene copolymer with ethylene with an ethylenecontent of from about 1% to about 6% by weight of the copolymer. Thestyrene and hydrocarbon copolymer is more preferably an SEBS tri-blockcopolymer as defined above. The polypropylene copolymer shouldconstitute from about 70% to about 95% and more preferably from about80% to about 90% of the blend, and the SEBS will constitute from about5% to about 30% and more preferably from about 10% to about 20% SEBS. Ina preferred form of the invention, the polypropylene used to fabricatethe cassette will have a lower melting point temperature than the highmelt strength polypropylene used to fabricate the membrane. In apreferred form of the invention the polypropylene of the cassette 160will have a melting point temperature of from about 120° C.-140° C. andfor the film from about 145° C.-160° C. The cassette 160 can beinjection molded from these polymer blends.

The upper and lower membranes 162, 164 are attached to the cassette 160utilizing heat sealing techniques. The film has a peel strength ofgreater than 5.0 lbf/inch when tested with a tensile instrument untilfilm failure or bond failure. Also, when the film is attached to thecassette it can be deformed under a pressure of 5 psi. The filmmaintains its low modulus and deformability properties even aftersterilization to continue to meet the pumping requirement. The film hasan extended shelf life. The film retains its pumping abilities evenafter two years shelf storage.

IV. Valve Actuator

Referring now to FIG. 15, one embodiment of an interface between thevalve actuator 26 and the valve manifold 190 is illustrated. The valvemotor 28 (not illustrated) of the valve actuator 26 drives a camshaft200 through a mechanical linkage determinable to those of skill in theart. In an embodiment, a single camshaft 200 attaches to a series ofcams 202, for example, one of each of the valves in the system 10 or100. The cams 202 are fixed to the camshaft 200 and rotate in a one toone relationship with same.

The cams 202 drive pistons 204, which engage in a friction reduced waywith the cams, for example, via rollers 206. The cams 202 drive pistons204 up and down (only two of five cams shown having associated pistonsto show other features of the actuator 26). When a cam 202 drives itsassociated piston 204 upward, the piston 204 engages one of themembranes 162 or 164 (typically the lower membrane 164, which is notshown in FIG. 15 for clarity) and pushes the membrane up into therespective hole 192 defined by the rigid manifold 190. This action stopsthe flow of medical fluid or dialysate through the respective valve.

The pistons 204 are also spring-loaded inside a respective housing 208.When the camshaft 200 turns so that a lower cam profile appears belowone of the pistons 204, the spring inside the housing 208 pushes thepiston 204 so that the roller 206 maintains contact with the respectivecam 202. The piston 204 consequently moves away from the respective hole192 defined by the rigid manifold 190, wherein the membrane 162 or 164,which has been stretched upward by the piston 204, springs back to itsnormal shape. This action starts the flow of medical fluid or dialysatethrough the respective valve.

The motor 28 is of a type, for example a stepper or servo motor, thatcan rotate a fraction of a rotation and stop and dwell for anypredetermined period of time. Thus, the motor 28 can hold a valve openor closed for as long as necessary. The cams 202 are shaped to provide aunique combination of bumps and valleys for every flow situation. Incertain situations, such as with valves V2 and V3 of the system 10, thevalves always open and close together, so that both valves use the samecam 202 oriented in the same way on camshaft 200.

Referring now to FIGS. 16A and 16B, the camshaft 200 and cams 202 areillustrated figuratively. FIG. 16A illustrates a composite cam profile370, i.e., a combination of each of the cams 202 a to 202 f illustratedin FIG. 16B. FIG. 16B illustrates that the cams 202 a to 202 f mount tothe camshaft 200 via hubs 384. The hubs 384 may employ set screens as iswell known. camshaft 200 can also have indentations, etc., for aligningthe hubs 384. In an alternative embodiment, one or more of the cams 202a to 202 f may be integrally formed with the otherwise camshaft 200. Inan embodiment, the camshaft 200 is a single molded piece, which preventsthe cams 202 a to 202 f from rotating with respect to one another. Thesingle molded camshaft 200 supports or attaches to a plurality of or toall of the cams 202 a to 202 f.

As illustrated above in FIG. 15, each of the cams 202 a to 202 f of FIG.16B drives a single piston 204 and roller 206 to operate a single valvehead 192 of the rigid manifold 190. The cams 202 a to 202 f open orocclude the valve heads 192 according to the shape of the respectivecam. FIG. 16B illustrates that the camshaft 200 supports six cams 202 ato 202 f. FIG. 15 illustrates five cams 200. The cam provided in theembodiment of FIG. 16B may be to open a last bag, illustrated by the“last bag valve open” position 382. Either of the systems 10 or 100 mayinclude a last bag. The last bag is a final dialysate fill of about twoliters into the patient before the patient disconnects from the systemand resumes normal daily activities.

The valve motor 28 and the valve actuator 26 (FIGS. 1 and 2) rotate thecamshaft 200 to open or close the valve heads 192 to create a desiredsolution flow path. The arrangement of the cams 202 a to 202 f on thecamshaft 200 is made such that, at any time during the therapy, there isno more than one fluid path open at any given time. Further, when thevalve actuator 26 rotates the camshaft 200 from one flow path openposition to the next, the series of cams 202 a to 202 f close all thevalves for a moment of time. The closing of each of the valves preventsdialysate from back-flowing or moving in the wrong direction. Stillfurther, the cams 202 a to 202 f are arranged such that only one valvehead 192 of the valve manifold 190 of the disposable unit 160 may beopen at any given time. Therefore, there is no open fluid path in theevent of a system failure or inadvertent power down. This safety featureprevents dialysate from free-flowing into the patient 12 or overfillingthe patient 12.

The lid 116 for the housing 112 of the hardware unit 110 may be freelyopened by an operator or patient to load the disposable unit 160 intothe hardware unit. When this occurs, the controller 30 automaticallycommands the camshaft to rotate so that an “all valves open” position372, illustrated by the composite profile 370, resides beneath therollers 206 and pistons 204. In the “all valves open” position 372, thecamshaft 200 is rotated such that a depression exists under each of thepistons 204 and associated rollers 206. Accordingly, the pistons 204 sitin a relatively low position, i.e., out of the way, when the operator orpatient loads the disposable unit 160 and valve manifold 190 into thehardware unit 110. This enables the patient or operator to place adisposable unit 160 into the unit 110 without encountering anobstruction or opposing force by one or more of the pistons 206.

After the patient or operator loads the disposable unit into thehardware unit 110 and closes the lid 116, the controller 30automatically rotates the camshaft 200 so that an “all valves closed”position 386 a resides beneath the pistons 204 and rollers 206. Asillustrated, the “all valves closed” position 386 a resides adjacent tothe “all valves open” position 372. When the camshaft 200 is rotated tothe “all valves closed position” 386 a, no fluid can flow through thesystem 10, 100. As the camshaft 200 rotates from the “all valves open”position 372 to the first “all valves closed” position 386 a, amechanical interlock (not illustrated) is moved into the camshaft 200,which prevents the rotation of the camshaft 200 back to the “all valvesopen” position 372. This prevents uncontrolled flow of the dialysate,which could occur when each of the valve heads 192 is open, in the eventthat the operator tries to open the lid 116 during therapy.

In an alternative embodiment, an interlock can be provided throughsoftware. An encoder provides positional and velocity feedback to thecontroller 30. The controller 30 therefore knows the position of the camshaft 200. Thus, the controller 30 is able to prevent the rotation ofthe camshaft 200 back to the “all valves open” position 372.

When the patient closes lid 116, a second mechanical interlock (notillustrated) locks the lid in place, so that the patient cannot open thelid 116 during therapy. The system 10, 100 senses when the patient hasremoved the patient fluid line 292 and connector 290 from the transferset, which is implanted in the patient 12. Only then will the system 10,100 allow the patient to open the lid 116. The mechanical interlocksprevent free-filling, overfilling and the patient from tampering withthe system while it is running. The valve configuration provides a failsafe system that prevents fluid flow in the event of a failure or powerdown.

In many instances, when the patient begins dialysis therapy, the patientis already full of dialysate. In the illustrated embodiment of FIG. 16A,therefore, the composite profile 370 provides the “all valve open”position 372 next to the “from patient value open” position 374. The“from patient valve open” position resides next to the “drain valveopen” position 376. In this manner, upon therapy startup, camshaft 200is readily positioned to be able to cooperate with the pump 20, 120 todrain spent dialysate from the patient. It should be appreciated thatany of the cams 202 a to 202 f may be the cam that provides the “frompatient valve open” position 374, the “drain valve open” position 376,etc.

Between the “from patient valve open” position 374 and the “drain valveopen” position 376 resides a second “all valves closed” position 386 b.Between each opening of a new valve and closing of a previously openedvalve, each valve is momentarily closed. The controller 30 causes themotor (e.g., a stepper, servo or DC motor) and actuator 26 to toggle thecamshaft 200 back and forth between the “from patent valve open”position 374, past the “all valves closed” position 386 b, to the “drainvalve open” position 376. In this manner, the pump 20, 120 is able tosequentially pull apart fluid from the patient 12 and dump it to drain18.

When the system 10, 100 completes the initial patient drain cycle, thecontroller 30 causes the actuator 26 of motor 28 to rotate camshaft 200past the “all valves closed” position 386 c to the “supply valve openposition” 378. To fill the patient full of fresh dialysate, thecontroller 30 causes the camshaft 200 to toggle back and forth betweenthe “supply valve open” position 378 and the “to patient valve open”position 380, each time passing over the “all valves closed” position386 d. Again, for the drain and fill cycles, only one valve head 192 isopen at any given period of time. The toggling always includes an “allvalves closed” position between the dosing of one valve head 192 and theopening of another. The single pump sequentially pulls fluid into thedisposable unit 160 and pushes fluid from same.

After the initial fill, camshaft 200 is positioned so that the camshaft200 can once again toggle back and forth between the “from patient valveopen” position 374, past the intermediate “all valves closed” position386 b, to the “drain valve open” position 376. When the patient is onceagain empty, the camshaft 200 is positioned so that the camshaft may betoggled back and forth between the “supply valve open” position 378 andthe “to patient valve open” position 380. The system 10, 100 repeatsthis series of cycles as many times as necessary. Typically, the patientreceives approximately 2 to 2.5 liters of dialysate in a single fillcycle. The two supply bags 14 each hold six liters of dialysate in anembodiment. This provides the system 10, 100 with four to six completefill, dwell and drain cycles, which are provided, for example, throughthe night while the patient sleeps.

In many instances, the patient will receive a last bag fill at the endof the therapy, which the patient will carry for the day. To performthis procedure, the camshaft 200 toggles back and forth between the“from patient valve open” position 374 to the “drain valve open”position 376 to dump the preceding fill of peritoneal fluid to drain 18.Thereafter, the camshaft 200 is positioned to toggle back and forthbetween the “last bag valve open” position 382 and the “to patient valveopen” position 380. In doing so, the camshaft 200 rotates past one ofthe all valves closed positions, namely, the “all valves closedposition” 386 e.

To prime the system, the camshaft 200 may be positioned and toggled in anumber of different ways. In one embodiment, the camshaft 200 togglesback and forth between the “supply valve open” position 378 and the“drain valve open” position 376, passing over the “all valves closed”position 386 c. This toggling in cooperation with the pumping of pump 20or 120 causes the dialysate to flow from the supply bags 14, through thedisposable unit 160, to drain 18. In another embodiment, using thevented tip protector 280 illustrated in connection with the FIGS. 8 to12, the camshaft 200 toggles back and forth between the “supply valveopen” position 378 and the “to patient valve open” position 380. Thiscauses dialysate to flow from the bags 14, through the disposable unit160, and into the patient fluid line 292 to the end of the vented tipprotector 280. When dialysate reaches the hydrophobic membrane 300 ofthe vented tip protection 28, the pressure in the system 10, 100 rises,wherein a signal is received by the controller 30, which causes the pump20, 120 to stop pumping and the camshaft 200 to stop toggling.

V. Medical Fluid Pump A. Pump Hardware and Operation

Referring now to FIGS. 17A and 17B, one embodiment of the pump 20 isillustrated. The lid 116 of the hardware unit 110 defines an upperchamber wall 216. Disposed within the housing 112 of the hardware unit110 (FIGS. 3A to 4B) is a lower chamber wall 218. The chamber walls 216and 218 define an internal chamber 210. The chamber 210 can have anydesired shape, for instance the clamshell shape as illustrated in FIGS.17A and 17B.

The lower chamber wall 218 defines or provides a sealed aperture 219that allows a pump piston 212 to translate back and forth within thechamber 210. The piston 212 is attached to or integrally formed with apiston head 214. The piston head 214 in an embodiment has an outer shapethat is similar to or the same as an internal shape of the upper chamberwall 216.

The pump piston 212 connects to or is integrally formed with the linearactuator 24. The linear actuator 24 in an embodiment is a device, suchas a ball screw, that converts the rotary motion of a motor 22 into thetranslational motion of the piston 212. In one embodiment, the motor 22is a linear stepper motor that outputs a translationally moving shaft.Here, the actuator 24 may simply couple the motor shaft to the piston212. The linear or rotary stepper motor provides quiet linear motion anda very high positional resolution, accuracy and repeatability. Steppermotors are commercially available, for example, from Hayden Switch andInstrument Inc., Waterbury, Conn.

As described above, the flexible fluid receptacle 172 (seen in FIG. 17Abut not in FIG. 17B) is defined by the expandable upper and lowermembranes 162 and 164, respectively, of the disposable unit 160. In FIG.17A, when the pump 20 is full of medical fluid, the pump chamber 210 andthe membrane receptacle 172 have substantially the same shape. In FIG.17B, when the pump 20 has displaced all or most all of the medicalfluid, the pump chamber 210 maintains the same volume but the membranes162 and 164 of the fluid receptacle 172 have collapsed to virtually azero volume along the interior surface of the upper chamber wall 216.

Vacuum source 44 for the pump 20 is described above in connection withFIG. 1. The vacuum source 44 exerts a vacuum on the upper membrane 162,through the aperture or port 222. The aperture or port 222 extendsthrough the upper chamber wall 216. The vacuum source 44 exerts a vacuumon the lower membrane 164, through an aperture 221 defined or providedby housing 223, and through the port or aperture 220. The port oraperture 220 extends through the piston 212, including the piston head214. When a vacuum is applied, the lower membrane 164 seals against thepiston head 214. The upper membrane 162 seals against the upper chamberwall 216.

The port 222 fluidly connects to channels (not illustrated) defined bythe interior wall of the upper chamber wall 216. The channels extendradially outwardly from port 222 in various directions. The channelshelp to distribute the negative pressure applied through the port 222 tofurther enable the upper membrane 162 to substantially conform to theinterior shape of the upper chamber wall 216. In a similar manner, theouter surface of the piston head 214 can include radially extendingchannels to further enable the lower membrane 164 to substantiallyconform, upon application of the vacuum, to the outer surface of thepiston head 214.

The pump 20 also includes a diaphragm 232 tensioned between the upperand lower chamber walls 216 and 218, respectively. The diaphragm 232defines, together with the upper chamber wall 218, a known, predictableand repeatable maximum volume of dialysate, which can be drawn from oneor more of the supply bags 14 and transported to the patient 12. Thediaphragm 232 also enables the volume of a partial stroke to becharacterized, which also enables accurate and repeatable volumemeasurements.

The diaphragm 232 is disposed beneath the piston head 214 and around thepiston 212. When the vacuum is applied to the port or aperture 220, thediaphragm 232, as well as the lower membrane 164, are pulled against thepiston head 214. When the piston head 214 is actuated upwardly away fromthe lower chamber wall 218, with the vacuum applied through aperture220, the membrane 164 and the diaphragm 232 remain drawn to the pistonhead 214. An inner portion of the membrane 164 conforms to the shape ofthe outer surface of the piston head 214. The remaining outer portion ofthe membrane 164 conforms to the shape of the exposed surface of thediaphragm 232.

The diaphragm 232 in an embodiment includes a flexible, moldedcup-shaped elastomer and a fabric reinforcement, such as fabricreinforced ethylene propylene diene methylene (“EPDM”). The fabric canbe integrally molded with the elastomer. The fabric prevents unwanteddeformation of the diaphragm while under pressure. The diaphragm 232 canstretch when the piston 212 and head 214 move downwardly towards thelower chamber wall 218, pulling the diaphragm 232 along the crimpededges of the upper and lower chamber walls 216 and 218. The diaphragm232 also moves and remains sealed to the piston head 214 when the piston212 and head 214 move upwardly towards the upper chamber wall 216.

In operating the pump 20, negative pressure is constantly appliedthrough the port 222 to hold the upper membrane 162 against the upperchamber wall 216. The manifold 190 of the disposable unit 160 (see FIGS.3A and 5) define a fluid port opening 230 to the membrane receptacle172. The fluid port opening 230 allows medical fluid or dialysate toenter and exit the membrane receptacle 172. The membrane receptacle 172seats in place with the crimped edges of the upper and lower chamberwalls 216 and 218. The seal 170 of the receptacle 172 may actuallyreside slightly inside the crimped edges of the upper and lower chamberwalls 216 and 218 (see FIG. 4A).

During a pump fill stroke, with the upper membrane 162 vacuum-pressedagainst the upper chamber wall 216, and the lower membrane 164 and thediaphragm 232 vacuum-pressed against the piston head 214, the motor22/actuator 24 cause the piston head 214 to move downwardly towards thelower chamber wall 218, increasing the volume within the flexiblereceptacle 172, and producing a negative pressure within same. Thenegative pressure pulls dialysate from the supply bags 14 or the patient12 as dictated by the current valve arrangement. The opened receptacle172 fills with fluid. This process occurs when the pump moves from theposition of FIG. 17B to the position of FIG. 17A. FIG. 17A shows thepump 20 at the end of the stroke, with the receptacle 172 fully opened(i.e., full of fluid).

During a patient fill or drain stroke, again with the upper membrane 162vacuum-pressed against the upper chamber wall 216, and the lowermembrane 164 and the diaphragm 232 vacuum-pressed against the pistonhead 214, the motor 22/actuator 24 cause the piston head 214 to moveupwardly towards the upper chamber wall 216, decreasing the volumewithin the flexible receptacle 172 and producing a positive pressurewithin same. The positive pressure pushes dialysate from the receptacle172 to the patient 12 or the drain 18 as dictated by the current valvearrangement. The receptacle 172 closes as the lower membrane 164 movesupward towards the upper membrane 162. This process occurs when the pumpmoves from the position of FIG. 17A to the position of FIG. 17B. FIG.17B shows the pump 20 at the end of the stroke, with the receptacle 172empty or virtually empty.

In the event that air (“air” for purposes of this invention includes airas well as other gases which may be present, particularly those thathave escaped from the patient's peritoneal cavity) enters the fluidreceptacle 172, it must be purged to maintain accuracy. It should beappreciated that if air enters between the membranes 162 and 164, system10, 100 in one embodiment does not have the ability to pull a vacuumbetween the membranes 162 and 164. The elasticity of the membranes 162and 164, however, naturally tend to purge air therefrom. In analternative embodiment the system 10, 100 can be adapted to provide avacuum source that pulls a vacuum between the membranes 162 and 164 topurge air therefrom.

To purge air from between the membranes, the system 10, 100 alsoprovides a positive pressure source. In systems 10, 100, for example,the pump motor 46 can be used in reverse of normal operation and,instead of producing vacuum source 44 (FIGS. 1 and 2), produce apositive pressure. The system 10 applies a positive pressure through theaperture or port 222 in the upper chamber wall 216 when air is detectedbetween the membranes 162 and 164 or elsewhere in the disposable unit160 or tubing. In one purge procedure, the controller 30 causes themotor 22/actuator 24 to move the piston head 214 to approximately ahalfway point in either the positive or negative strokes. With the uppermembrane 162 vacuum-pressed against the upper chamber wall 216, and thelower membrane 164 and the diaphragm 232 vacuum-pressed against thepiston head 214 maintained at the halfway point, the controller causesthe negative pressure source in through the aperture 222 to change to apositive pressure source, which pushes the upper membrane 162conformingly against the lower membrane 164, which is supported by thepiston head 214 and the diaphragm 232. Any air or fluid residing in thereceptacle 172 is purged to drain as is any air between the receptacle172 and drain 18.

B. Capacitance Volume Sensor

FIGS. 17A and 17B also illustrate that the pump 20 cooperates with anembodiment of the capacitance fluid volume sensor 60 of the system 10.One embodiment of a capacitance sensor 60 is disclosed in greater detailin the patent application entitled, “Capacitance Fluid VolumeMeasurement,” Ser. No. 10/054,487, filed on Jan. 22, 2002, incorporatedherein by reference. The capacitance sensor 60 uses capacitancemeasurement techniques to determine the volume of a fluid inside of achamber. As the volume of the fluid changes, a sensed voltage that isproportional to the change in capacitance changes. Therefore, the sensor60 can determine whether the chamber is, for example, empty, an eighthfull, quarter full, half full, full, or any other percent full. Each ofthese measurements can be made accurately, for example, at least on theorder of the accuracy achieved by known gravimetric scales orpressure/volume measurements. The present disclosure, however, issimpler, non-invasive, inexpensive and does not require the medicaloperation to be a batch operation.

Generally, the capacitance C between two capacitor plates changesaccording to the function C=k×(S/d), wherein k is the dielectricconstant, S is the surface area of the individual plates and d is thedistance between the plates. The capacitance between the plates changesproportionally according to the function 1/(R×V), wherein R is a knownresistance and V is the voltage measured across the capacitor plates.

The dielectric constant k of medical fluid or dialysate is much higherthan that of air, which typically fills the pump chamber 210 when thepiston head 214 is bottomed out against the upper chamber wall 216, asillustrated in FIG. 17B. Therefore, the varying distance, Δd, of the lowdielectric displacement fluid between the expanding and contractingreceptacle 172 and the lower chamber wall 218 may have some effect onthe capacitance between ground capacitance plate 224 and the activecapacitance plate 226. Likewise the surface area, S, of the capacitanceplates and the moving membrane 164 may have some effect on thecapacitance. Certainly, the changing overall dielectric from the highdielectric dialysate replacing the low dielectric air (or vice versa)affects the overall capacitance between the plates 224 and 226.

As the membranes 162 and 164 expand and fill with medical fluid, theoverall capacitance changes, i.e., increases. The sensor 60 generates ahigh impedance potential across the grounded and active capacitor plates224 and 226. The high impedance potential is indicative of an amount offluid in the receptacle 172. If the potential does not change over timewhen it is expected to change, the sensor 60 can also indicate an amountor portion of air within the receptacle 172.

A capacitance sensing circuit amplifies the high impedance signal toproduce a low impedance potential. The low impedance potential is alsofed back to the guard plate 228, which protects the sensitive signalfrom being effected by outside electrical influences. The amplifiedpotential is converted to a digital signal and fed to the processor 34,where it is filtered and/or summed. The video monitor 40 can then beused to visually provide a volume and/or a flowrate indication to apatient or operator. Additionally, the processor 34 can use the summedoutputs to control the pump 20 of the system 10, for example, toterminate dialysate flow upon reaching predetermined overall volume.

Referring now to FIG. 18, the pump 120 of the system 100 is illustratedin operation with the capacitance sensor 60 of the present disclosure.The pump 120 forms a clamshell with first and second portions 246 and248, which together form the pump chamber 250. The portions 246 and 248are rigid, fixed volume, disked shaped indentations in the base 114 andlid 116 of the hardware unit 110. The clamshell first and secondportions 246 and 248 are closed and sealed on the pump receptacleportion 172 of the disposable unit 110, which includes the expandablemembranes 162 and 164.

An opening or aperture 252 is defined between the first and secondclamshell portions 246 and 248 and the flexible membranes 162 and 164.The opening 252 enables medical fluid, for example, dialysate, to enterand exit the chamber 250 between the membranes 162 and 164 in thereceptacle portion 172. The receptacle portion 172 fluidly communicateswith the valve manifold 190.

FIG. 18 shows the pump chamber 250 in an empty state with both membranes162 and 164 in relaxed positions, so that the flexible receptacleportion 172 is closed. The empty volume state is achieved when themembranes 162 and 164 have collapsed so that substantially all the fluidis removed from the sterile receptacle 172 and likewise the pump chamber250.

The empty volume state can be achieved, for example, by allowing theelastic membranes 162, 164 to return to their relaxed, unstressed stateas shown in FIG. 18. Also, both membranes 162 and 164 can be forcedtogether against each other or against either one of the inside portions246 and 248 of the pump chamber 250. When the pump chamber 250 is in thefull state, the medical fluid resides between the membranes 162 and 164,wherein the membranes have been suctioned against the inner walls ofportions 246 and 248.

It should be appreciated that either one or both of the membranes 162and 164 can be moved towards and away from the clamshell portions 246and 248 by any suitable fluid activation device. In various embodiments,the diaphragm pump is pneumatically or hydraulically actuated.

The diaphragm pump 120 of the system 100 does not require a separatepiston or mechanical actuator as does the pump 20 of the system 10. Theclamshell portions 246 and 248 define ports 254 and 256, respectively,to allow for movement of a displacement fluid (for example, pneumatic orhydraulic fluid) into and out of the chamber areas outside of thereceptacle 172 to operate the diaphragm pump.

In an embodiment, the medical fluid, for example, dialysate, issuctioned into the receptacle 172 in the chamber 250. The receptacle172, defined by membranes 162 and 164, may be filled with medical fluidby applying negative pressures to one or both of the chamber ports 254and 256. The medical fluid can be emptied from the receptacle 172 byapplying a positive pressure to at least one of the ports 254 and 256,or by allowing the membranes 162 and 164 to spring back into shape. Inan alternative embodiment, the medical fluid, for example, dialysate, ispressurized from an external source to move in and out of the pumpchamber 250 between the membranes 162 and 164.

The clamshell portions 246 and 248 form and hold the capacitor plates ofthe capacitance sensor 60. In an embodiment, upper clamshell portion 246includes an active metal or otherwise conductive capacitance plate 258between electrically insulative or plastic layers. A metal guard plate260 is provided on the outer plastic layer of the upper clamshellportion 246. The guard plate 260 provides noise protection for the highimpedance signal that transmits from the active capacitor plate 258.

As with the pump 20 of system 10, the active capacitor plate 258 ofupper clamshell portion 246 of the pump 120 of the system 100electrically couples to a capacitance sensing circuit. The guard plate260 likewise electrically couples to the feedback loop of thecapacitance sensing circuit as described above.

In an embodiment, lower clamshell portion 248 is also made of an inertplastic, wherein a metal capacitor plate 262 attaches to the outersurface of the lower clamshell portion 248. The metal capacitor plate262 disposed on the outside of the clamshell portion 248 electricallycouples to ground.

In one implementation, a negative pressure is constantly maintained atthe lower port 256, so that the lower membrane 164 is pulled to conformto the inner surface of the grounded clamshell portion 248 during amultitude of fill and empty cycles. In this implementation, the uppermembrane 162 does the pumping work. That is, when a negative pressure isapplied to upper port 254 of upper clamshell 246, upper membrane 162 issuctioned up against and conforms with the inner surface of upperclamshell 246. This action draws fluid from the supply bag 14, throughthe manifold 190, and into the receptacle 172. To expel fluid, thenegative pressure is released from upper port 254, wherein uppermembrane 162 collapses to push the fluid from the receptacle 172.Alternatively, a positive pressure is applied through one or both ports.

In operation, the capacitance sensor 60 operates substantially asdescribed in FIGS. 17A and 17B. The receptacle 172 expands between theportions 246 and 248. A varying distance, Δd, of the low dielectricdisplacement fluid between the expanding and contracting receptacle 172and the portions 246 and 248 may have some effect on the capacitancebetween the ground plate 262 and the active plate 258. Likewise thesurface area, S, defined by the ground and active capacitance plates andthe expanding membranes may have some effect on the overall capacitance.Certainly, the changing overall dielectric from the high dielectricdialysate replacing the low dielectric air (or vice versa) affects theoverall capacitance between the plates 258 and 262.

As the membranes 162 and 164 expand and fill with medical fluid, thecapacitance changes, i.e., increases. Each different amount of medicalfluid within the chamber 250 has a unique overall capacitance. A uniquecapacitance value can therefore be associated with each specific fluidvolume in the chamber, for example, substantially empty, partially full,or substantially full.

As an alternative to the capacitance volume sensor 60 described above,the volume of dialysate fluid flowing through the automated systems 10and 100 can be determined using other methods, such as through anelectronic balance. In such a case, the electronic balance keeps trackof the amount of dialysate that is supplied to the system during apriming of the system. The electronic balance also monitors anyadditional dialysate added to the system during dialysis treatment.

In other alternative embodiments, any of the systems described hereincan be sensed using other types of flowmeters or devices employingBoyle's Law, which are known to those of skill in the art. Further,various other types of fluid volume measurement or flowrate devices canbe used with the automated systems 10 and 100, such as orifice plates,mass flow meters or other flow measuring devices known to those of skillin the art.

VI. Precision Pressure Control

As discussed above, the system 10 employs a valve actuator 24 and a pumpmotor 22. In one embodiment the pump motor 22 is a stepper motor. Inanother embodiment, the motor 22 may be a DC motor or other type ofrepeatable and accurately positionable motor. Each of these types ofmotors enable system 10 to position the piston 212 and piston head 214very accurately within the pump chamber 210. In the case of a highprecision rotary motor 22, the actuator 24 converts the rotary motioninto a translation motion precisely and moves the piston 212 back andforth within the chamber 210 within the accuracy and repeatabilityrequirement of the system. The resolution of the linear stepper motor inan embodiment is about 0.00012 inches per step to about 0.00192 inchesper step.

The pump motor 22 is also programmable. The programmable nature of thepump motor 22 enables acceleration, velocity and positional data to beentered into the controller 30, wherein the controller 30 uses theinformation to position the piston 212 and piston head 214 within thepump chamber 210, within an appropriate amount of time, to produce adesired amount of force or fluid pressure. The ability to preset theacceleration, velocity and position of the piston head 214 provides anadvantage over purely pneumatic systems that respond relativelysluggishly to pneumatic signals.

The flexible nature of the PVC medical tubing described, e.g., inconnection with FIG. 8 and the membrane material, described above inconnection with FIGS. 13 and 14, causes the system 10 to have what isknown as “compliance”. Compliance is caused when the system 10 attemptsto create fluid pressure, e.g., by moving the pump piston 212 and head214, but instead causes the flexible tubing and membranes to expand.With the flexible tubing and membranes, compliance is inevitable.Eventually, when the tubing and membranes have expanded to their elasticlimit, the pressure in the pump chamber 210 (i.e., in the receptacle172) and throughout the tubing rises sharply. It is desirable toovercome the compliance of the tubing and membranes 162 and 164 asquickly as possible so that pressure may be built to drive the fluid.

The present disclosure uses a hybrid pressure control system thatcombines the ability to preset the pump piston acceleration and velocitywith an adaptive pressure control scheme, which causes the pressure toachieve a desired pressure set point for any given stroke and causes thepressure to be fine tuned over time, i.e., over repeated strokes. Thatis, the present disclosure employs a method of controlling pressurewithin the system that seeks first to overcome system compliance andthen seeks to achieve a desired pressure set point. The output of thepresent method of controlling pressure within the pump chamber 210 isillustrated by the velocity and pressure curves of FIG. 19.

In general, the system 10 controls the pressure within the receptacle172 in the pump chamber 210 by controlling the velocity of the piston212 and piston head 214. The velocity profile 390 of FIG. 19 illustratesa single pump stroke that occurs over a time “t” beginning at the startof stroke position 392. In the beginning of the stroke, the velocityramps up at a preset acceleration 394. The preset acceleration 394 isprogrammed into the controller 30. When the velocity due to the presetacceleration 394 reaches a max velocity 396, the acceleration 394changes to a zero acceleration, and the piston 212 moves at the constantmax velocity 396.

During the time period of the acceleration 394 and the max velocity 396,which is designated by the dashed vertical line 398, the correspondingpressure as illustrated by a pressure curve 401 of pressure profile 400,ramps up beginning very slowly and exponentially increasing as the timereaches that of the dashed line 398. In the initial portion of thepressure curve, i.e., just after the start of stroke position, thepressure builds slowly as the compliance in the system is taken up. Asthe compliance is taken up, the pressure builds at faster and fasterrates.

When the pressure reaches a pressure proximity threshold 402, set insoftware, the software within the controller 30 converts from theprevious motion (acceleration, velocity, position) control to anadaptive control. It should therefore be appreciated that the method ofcontrolling pressure within the fluid pump of the present disclosure isa hybrid type of control method, employing a combination of techniques.

The motion control portion, accented by the acceleration 394 and maxvelocity 396, represents a period in time when the method of control isforcing the system to overcome the pressure compliance. Upon reachingthe pressure proximity threshold 402, the controller 30 causes thevelocity to sharply decelerate at deceleration 404. Deceleration 404reduces the velocity of the piston 212 and piston head 214 to a velocity406, which is a velocity that aids in the ability of the adaptivecontrol portion of the pressure control system to achieve a pressure setpoint 408. That is, without the programmed deceleration 404, theadaptive control portion would have a more difficult (i.e., longer) timecontrolling the velocity to make the pressure reach or substantiallyreach the pressure set point 408.

As explained in more detail below, the acceleration 394 is adaptivelycontrolled in an embodiment, so as to reduce the amount of initialovershoot. The adaptive control over the acceleration 394 is fine tunedover time to further reduce the amount of initial overshoot. Each ofthese measures affects the amount of controlled deceleration 404 needed.

After the controlled deceleration 404 reaches the velocity 406 and untilthe time of the second dashed line 410, the system 10 operates in anadaptive mode. The second vertical line 410 occurs near the end of thestroke. As illustrated, the adaptive portion of the stroke is brokendown into a number of areas, namely area 412 and area 414. Area 412 ischaracterized by the overshoot or undershoot caused by the programmedacceleration 394. In applying adaptive techniques, the adjustments orparameters that overcome area 414 error are tailored in software tocombat overshoot or undershoot. The area 414 focuses on attempting tominimize the error between the actual pressure curve 401 and thepressure set point 408. During the area 414, the parameters and adaptivemeasures are tailored in software reduce the oscillation of the pressurecurve 401 to achieve a pressure set point 408 as much as possible and asquickly as possible.

Upon reaching the time denoted by the dashed line 410, the pressurecontrol method once again resumes motion control and decelerates thevelocity at a controlled and predetermined deceleration 416 down to afinal travel velocity 418, which is also the initial velocity at thestart of the stroke 392. In an alternative embodiment, the method cansimply let the adaptive control continue past the time line 410 andattempt to achieve the final travel velocity 418. After the time line410, the pressure along pressure curve 401 falls off towards zeropressure as illustrated by the pressure profile 400. Comparing thepressure profile 400 to the velocity profile 390, it should beappreciated that pressure remains in the receptacle 172 of the pumpchamber 210 even after the stroke ends at time “t”. In some cases, thepressure overshoots as the piston 212 suddenly stops, wherein themomentum of the liquid produces a pressure spike after time “t”.

Referring now to FIG. 20, an algorithm 420 for employing the adaptivepressure control during the areas 412 and 414 of the pressure profile400 is illustrated. In an embodiment, the adaptive control portion ofthe pressure control method employs a proportional, integral andderivative (“PID”) adaptive parameters. In the method, a pressurereading is taken from a pressure sensor which senses the pressure insidethe receptacle 172 of the pump chamber 210, and which provides apressure sensor input 422 to the controller 30, as illustrated by thealgorithm 420. Pressure sensor input 422 is sent through a digitalfilter 424, producing a measured variable 426. The measured variable 426is compared with a desired variable, i.e., the pressure set point 408illustrated in FIG. 19, wherein an error 428 is produced between themeasured variable 426 and the desired pressure set point 408.

Next, the error 428 is entered into a PID calculation 430, which uses aproportional coefficient 432, an integral coefficient 434 and adifferential coefficient 436. The output of the PID calculation 430 isan adaptive pressure change 438. The controller 30 then changes thevelocity up or down to produce the pressure change 438.

In the pressure profile 400 of FIG. 19, the algorithm 420 of FIG. 20 isconstantly being performed during the adaptive areas 412 and 414. Asdiscussed below, the corrective parameters, e.g., the coefficients 432,434 and 436, are used differently during the areas 412 and 414 becausecorrection in the area 412 is focused on minimizing overshoot andundershoot, while correction in the area 414 however is focused onreducing error to zero about the pressure set point 408.

As described above, a single pump 20 is used in the system 10. Thesingle pump 20 provides positive pressure during the patient fill strokeand the pump to drain stroke. The pump 20 also provides negativepressure during the pull from supply bag 14 stroke and the pull frompatient 12 stroke. Of the four strokes, it is most important toaccurately control the pressure during the patient fill and patientdrain stoke. It is not as critical to control the pressure when pumpingfluid from the supply bags 14 or when pumping fluid from the receptacle172 of the pump chamber 210 to drain 18. In the two positive pressurestrokes, one stroke, namely the patient fill stroke, it is critical toproperly control pressure. In the two negative pressure strokes, one ofthe strokes, namely the pull from patient stroke, it is critical toproperly control pressure. In the other two strokes, pressure iscontrolled without taxing the controller, motor 22 and disposable unit160 needlessly.

Referring now to FIG. 21, pressure and velocity curves are shown for anumber of strokes during the patient fill cycle. The upper profile 440shows the actual pressure 444 versus the desired pressure 442 inmilli-pounds per square inch (“mPSI”). The lower profile 450 showscorresponding velocity curves. In the pressure profile 440, the darkenedline 442 corresponds to the desired pressure in mPSI. The curve 444illustrates the actual pressure in mPSI. The curves 452 a, 452 b and 452c in the velocity profile 450 illustrate the piston velocities thatproduce the pressure fluctuations along the pressure curve 444 of thepressure profile 440. The velocity is measured in some increment ofsteps per second, such as milli-steps per second or micro steps persecond when the motor 22 employed is a stepper motor. Different steppermotors for use in the present disclosure may be programmed in differentincrements of a step. The actual velocity is therefore a function of theresolution of the stepper motor.

At time zero, the desired pressure 442 changes virtually instantaneouslyto 2000 mPSI. The desired pressure curve 442 maintains this constant2000 mPSI until reaching approximately 1.6 seconds, at which point thedesired pressure 442 returns virtually instantaneously to zero. Thisstep by the desired pressure curve 442 represents one complete patientfill stroke, wherein one full positive up-stroke of the piston 212 andpiston head 214 within the pump chamber 220 occurs. In this step it iscritical to control pressure because dialysate is being pumped into thepatient's peritoneal cavity 12. The actual pressure curve 444 ramps upexponentially and oscillates about the 2000 mPSI set point in the mannerdescribed in connection with FIG. 19. It should also be noted that thevelocity curve 452 a follows a similar pattern to that shown in FIG. 19.

At about 1.6 seconds, i.e., when the piston head has reached the upperchamber 216 of the valve chamber 210, controller 30 stops the piston 212from moving. The velocity of the piston head remains at zero untilapproximately 3.4 seconds. In this period, the valves have all beenclosed via one of the “all valves closed” positions illustrated inconnection with FIG. 16A. As illustrated by pressure curve 444, residualfluid pressure resides within the pump chamber 210 even though thepiston head 214 is not moving.

At about time 3.4 seconds, the desired pressure curve 442 switchesvirtuously instantaneously to −2000 mPSI. The pump 20 is now being askedto expand and form a negative pressure that pulls fluid from the supplybags 14. During this stroke, it is not as critical to control pressureas accurately in the patient fill stroke. Accordingly, the method may beprogrammed to bypass the motion control portion of the pressure controlmethod and simply adaptively seek to find the pressure set point alongline 442. Dialysate moves through the fluid heating path 180 of thedisposable unit 160 (see FIGS. 3A and 5, etc.) during the patient fillstroke. Much of the compliance, i.e., stretching of the system occurswhen the fluid passes through the path 180. Pumping fluid from thesupply bag 14, however, does not require the fluid to pass through theheating path 180. The system 10 does not therefore experience the samelevel of compliance during this stroke. It is possible to pump from thebags 14 without using the motion control portion illustrated inconnection with FIG. 19, since the lessened compliance may not requirethe “brute force” supplied by the controlled acceleration.

In FIG. 21, the pump completes the stroke that pulls dialysate from thesupply bag at about five seconds. The demand pressure along curve 442returns to zero accordingly. Next, the valve switches to an all closedposition, the controller 30 sets the piston speed to zero, and thepiston head resides substantially along the lower chamber wall 218, withthe receptacle 172 full of fluid until approximately 6.8 seconds haspassed, wherein the system 10 repeats the patient fill stroke asdescribed previously.

Referring now to FIG. 22, a pressure profile 452 and a velocity profile460 are illustrated for the patient drain stroke and the pump to drainstroke of the patient drain cycle. In the pressure profile 452, thedemand pressure curve 454 illustrates that the controller calls for anegative 2500 mPSI to pull dialysate from the patient. The controller 30calls for a positive pressure of 2500 mPSI to push fluid from thereceptacle 172 of the pump chamber 210 to the drain bag 18. In thevelocity profile 460 shown below the pressure profile 452, the actualvelocity 462 in some increment of steps per second is illustrated. Itshould be appreciated that both velocity profiles 450 and 460 of FIGS.21 and 22 are absolute velocities and do not illustrate that the pumppiston 212 moves in positive and negative directions.

The actual pressure curve 456 of the profile 452 illustrates that thepressure is controlled to conform to the demand pressure line 454 moreclosely during the pull from patient portion than during the pump todrain portion of the profile 452. In an embodiment, the controller 30 isprogrammed to provide a motion controlled velocity 464 for a portion ofthe pull from patient stroke and use an adaptive control during the time“tadapt”. The method also uses, in an embodiment, a controlleddeceleration 466 at the end of the pull from patient stroke.Alternatively, the method allows the PID control to seek to find zeropressure. Similarly, during the pump to drain stroke, the controller 30can switch to PID control only.

Referring now to FIG. 23, one embodiment of an algorithm 470illustrating the “fine tuning” adaptive control of the PID portion ofthe pressure control method of the present disclosure is illustrated.FIG. 23, like FIG. 20, includes a measured pressure variable 426 and adesirable pressure set point 408. The pressure error 472 represents anerror in either the overshoot area 412 or the oscillation area 414illustrated in the pressure velocity profile 400 of FIG. 19. For eacharea, the algorithm 470 looks at two error components, namely, the error474 determined in the current stroke and the error 476 stored forprevious strokes. The controller 30 compares the two errors 476 and 478and makes a decision as illustrated in decision block 478.

In the block 476, if the current stroke error 474 is less than theprevious stroke error 476, the method uses the previous coefficientbecause the previous coefficient is currently having a desirable result.If the current stroke error 474 is greater than the previous strokeserror 476, two possibilities exist. First, the coefficient or correctivemeasure taken is not large enough to overcome the error increase. Here,the coefficient or corrective setting can be increased or another tacticmay be employed. Second, the previous corrective procedure may be havingan adverse impact, in which case the parameter connection can bereversed or another tactic can be employed. Obviously, to employalgorithm 470, the method provides that the controller 30 store themanner of the previous corrective attempts and outcomes of same. Basedon what has happened previously, the controller decides to increment ordecrease one or more of the parameters. The amount of increase ordecrease is then applied to one or more coefficients stored in anincrement table 480. The adjusted or non-adjusted increment is thensummed together with the currently used one or more coefficients 482 toform an adjusted one or more coefficients 484.

Referring now to FIG. 24, table 500 illustrates various differentcoefficients and adaptive perimeters for the pressure control method ofthe present disclosure. Certain of the coefficients and parameters applymore to the motion control portion of the profiles illustrated above,i.e., the set acceleration, deceleration and velocity portions of theprofiles. The motion control parameters, however, effect the error,which influences the adaptive parameters in the PID portion of thepressure control. Other parameters apply to the adaptive controlportions of the profiles. Adjusting the beginning stroke accelerationparameter 486 (illustrated by the acceleration 394 of the velocityprofile 390 of FIG. 19) affects the motion control portion of thepresent method. Acceleration as illustrated, affects overshoot and theefficient use of stroke time. That is, it is desirable to have a highacceleration to overcome compliance quickly, however, the cost may bethat overshoot increases. On the other hand, a lower acceleration mayreduce overshoot but require more time to overcome the compliance in thesystem.

The proximately threshold parameter 488 (illustrated by pressure line402 in the pressure profile 400 of FIG. 19) also affects overshoot andundershoot. Here, setting the pressure threshold 488 too low may causeundershoot, whereas setting the parameter 488 too high may causeovershoot. The DP/dt parameter 490 is the change in pressure for a givenperiod of time. This parameter seeks to achieve, for example in FIG. 19,a certain slope of the pressure curve 401.

The maximum travel velocity parameter 492, illustrated as line 396 inthe velocity profile 390 of FIG. 19, also affects overshoot andsubsequent resonance. Another corrective factor is the conversion topressure deceleration 494 corresponding to line 410 of FIG. 19. Themethod includes running the system without changing back to motioncontrol and instead leaving the system in the adaptive PID control. Theconversion to deceleration can have a large impact on the residualpressure remaining in the pump chamber 210 after the valves close.

The PID factors Kp, Kd and Ki, labeled 496, 498 and 502, respectively,affect the adaptive control portion of the present method but alsoaffect, to a lesser extent, the controlled declaration at the end of thestroke. Each of the PID factors or parameters can be changed and adaptedin mid-stroke. Also as illustrated in FIG. 23, the factors can bechanged so as to optimize the system over time.

Each of the above-described factors can be used to insulate the fluidpressure from changes in the environment outside of the system 10. Forexample, the factors can overcome changes due to physiological andchemical changes in the patient's abdomen. Also, the height of thepatient supply bags 14 affects the initial loading of the fluid pump 20.The parameters illustrated in FIG. 24 automatically overcome the changesdue to bag height. Further, as the patient sleeps through the night, thesupply bags 14 become less and less full, while the drain bag 18 becomesmore full, both of which affect the pump pressure. The parametersillustrated in FIG. 24 are automatically adjustable to compensate forthese changes and keep the system running smoothly.

Certain of the above-described factors is changed more and used moreduring the overshoot area 412 illustrated in the pressure profile 400 ofFIG. 19. Other factors and parameters are used and changed more duringthe oscillation portion 414 of the profile 400.

VII. In-Line Heater

In an embodiment, the inline heater 16 includes two electrical plateheaters, which are well known to those of skill in the art. The plateheaters of the heater 16 have a smooth and flat surface, which faces thedisposable unit 160. In an alternative embodiment, the automated systems10 and 100 provide an in-line heater 16 having a plate heater incombination with an infrared heater or other convective heater.

In the alternative dual mode type heater, both the plate heater and, forexample, the infrared heater are in-line heaters that heat the medicalfluid that flows through the fluid heating path 180 of the disposableunit 160. The radiant energy of the infrared heater is directed to andabsorbed by the fluid in the fluid heating path 180. The radiant energyor infrared heater in an embodiment is a primary or high capacityheater, which can heat a relatively large volume of cold fluid to adesired temperature in a short period of time.

The plate heater of the alternative dual mode heater in an embodiment isa secondary or maintenance heater which has a relatively lower heatingcapacity relative to the infrared heater. As described above, the plateheater uses electrical resistance to increase the temperature of a platethat in turn heats the fluid flowing though the path 180 adjacent to theplate.

The dual mode heater is particularly useful for quickly heating cooldialysate (high heat energy demand) supplied from one of the supply bags14 to the automated system 10 or 100. Initial system fills can be coolerthan later fills, and the system can lose heat during the dwell phase.The temperature of the dialysate at initial system fill can therefore bequite low, such as 5° C. to 10° C. if the supply bags 14 are stored incold ambient temperature.

The plate heater and the infrared heater of the dual mode heaterembodiment of the heater 16 can be arranged in various configurationsrelative to each other. The dual mode heaters in an embodiment arearranged so that the fluid passes by the heaters sequentially (e.g.,first the plate heater and then the radiant or infrared heater). Inanother embodiment, the fluid passes by the heaters simultaneously (bothheaters at the same time). The fluid flow path past the heaters can be acommon flow path for both heaters, such as in the fluid heating path180, or include independent flow paths for each heater.

VIII. Fuzzy Logic for Heater Control

Similar to the controlling of the fluid pressure, the control of theplate heater 16 is also subject to a number of environmental variables.For example, the ambient temperature inside the patient's home affectsthe amount of heat that is needed to raise the temperature of themedical fluid to a desired temperature. Obviously, the temperature ofthe dialysate in the supply bags 14 affects the amount of heat that isneeded to raise the fluid temperature to a desired temperature. Plateheater efficiency also affects the amount of heating needed. Further,the voltage provided by the patient's home is another factor. Typically,a doctor or caregiver prescribes the temperature of the dialysate forthe patient to be controlled to around a temperature of 37° C. It is,therefore, desirable to have a method of controlling the heater 16 tocorrect for outside temperature gradients so as to maintain the properpatient fluid temperature.

Referring now to FIG. 25, one embodiment of a heating control method 510is illustrated. The method 510 includes two separately performedalgorithms 520 and 530 that operate in parallel to form an overalloutput 544. The algorithm 520 is termed a “knowledge-based” controlalgorithm. The knowledge-based control algorithm is based on knowledge,such as empirical data, flow mechanics, laws of physics and lab data,etc.

The knowledge-based algorithm 520 requires a number of inputs as well asa number of constant settings. For example, the control algorithm 520requires an input pulsatile flowrate. As illustrated below, thepulsatile flowrate is actually calculated from a number of inputvariables. The system 10, 100 of the present disclosure provides fluidto the patient 12 in pulses, rather than on a continuous basis. Itshould be readily apparent from the discussion based on FIGS. 16A and16B, that when all valve heads in the disposable are closed, no fluidcan flow through the fluid heating pathway to the patient. The flowrateof fluid to the patient is therefore a pulsatile flowrate, wherein thepatient receives the dialysate in spurts or pulses. It is difficult tocontrol fluid temperature with this type of flowrate. To this end, themethod 510 provides the dual algorithms 520 and 530.

Besides the pulsatile flowrate, the knowledge-based control algorithm520 also receives a measured, i.e., actual, fluid inlet temperaturesignal. Further, the algorithm 520 stores the plate heater efficiency,which is based on empirical data. In one embodiment, the upper and lowerplates of the plate heater 16 are around 95% efficient. Algorithm 520also inputs the total heater power, which is derived from the voltageinput into the system 10, 100. Residential voltage may vary in a givenday or over a period of days or from place to place.

The algorithm 520 also inputs the desired outlet fluid temperature,which is a constant setting but which may be modified by the patient'sdoctor or caregiver. As illustrated in FIG. 25, the desired outlet fluidtemperature is inputted into both the knowledge-based control algorithm520 and the fuzzy logic based control algorithm 530. As discussed inmore detail below, the knowledge-based control algorithm 520 outputs aknowledge-based duty cycle into a summation point 544.

With respect to the fuzzy logic-based control algorithm 530, the desiredfluid temperature is inputted into a comparison point 514. Thecomparison point 514 outputs the difference between the desired fluidtemperature and the actual measured fluid temperature exiting theheating system 548. The fuzzy logic-based control algorithm 530therefore receives a change in temperature ΔT as an input. As describedbelow, the fuzzy logic-based control algorithm 530 employs the conceptsand strategies of fuzzy logic control to output a fuzzy logic dutycycle.

In the method 510, the knowledge-based duty cycle is adaptively weightedagainst the fuzzy logic-based duty cycle. In an alternative embodiment,the system predetermines a relative weight. In the method 510, the fuzzylogic-based duty cycle is weighted, i.e., provided a weight factor asillustrated in block 542. For example, if the fuzzy logic-based dutycycle is given a weight factor of one, then the fuzzy logic-based dutycycle is weighted equally with the knowledge-based duty cycle. If thefuzzy logic-based duty cycle is given a weight factor of two, the fuzzylogic-based duty cycle is given twice the weight as the knowledge-basedduty cycle. The weight factor in block 542 can change over time and/orbe optimized over time.

It should be appreciated that the weighting block 542 couldalternatively be placed in the knowledge-based duty cycle output. Asdiscussed below, however, the update rate of the fuzzy logic controlloop is substantially higher than the update rate of the input signalsentered into the knowledge-based control algorithm 520. It is thereforeadvantageous to weight the fuzzy logic-based duty cycle, as opposed tothe knowledge-based duty cycle.

The weighted fuzzy logic-based duty cycle and the knowledge-based dutycycle are summed together at summing point 544 to produce an overallheater duty cycle. Duty cycle is one way to control the power input and,thus, the plate temperature of the heater. Controlling the duty cyclemeans controlling the percentage of a time period that full power isapplied to the heater, for example, plate heater 16. In an alternativeembodiment, the output of the parallel control algorithms 520 and 530could be a percentage of full power applied at all times. Still further,the output of the parallel control algorithms 520 and 530 could be apercentage of full power applied for a percentage of a time period. Forpurposes of illustration, the method 510 is described using a duty cycleoutput which, as explained, is the percent of a time period that fullpower is applied to the heater.

As described herein, the heating system 548 (i.e., heater 16) in oneembodiment is a plate heater, wherein upper and lower plates aredisposed about a fluid heating path of the disposable unit 160. Itshould be appreciated, however, that the method 510 is equallyapplicable to the infrared heater previously described. Further, themethod 510 is equally applicable to the combination of different typesof heaters, such as, the combination of a plate heater and an infraredheater.

The method 510 uses multiple temperature sensors, such as the sensors 62illustrated in FIGS. 1 and 2, which sense the temperature at differenttimes within the method 510 and places within system 10,100. One sensorsenses the fluid outlet temperature, which feeds back from the heatingsystem 548 to the comparison point 514. Another two temperature sensorssense the temperature of the top plate and the bottom plate and feedback to the temperature limit controller 546, located in software.

As illustrated, before the summed heater duty cycle is inputted into theheating system 548, the system determines whether the top and bottomheating plates are already at a maximum allowable temperature. Thereexists a temperature above which it is not safe to maintain the platesof the plate heater. In a situation where one or both of the plates iscurrently at the temperature limit, the method 510 outputs a zero dutycycle, regardless of the calculations of the knowledge-based controlsystem 520 and the fuzzy logic-based algorithm 530. To this end, thetemperature of the top and bottom plates is fed back into the block 546,wherein the software only allows a heater duty cycle to be applied tothe heating system 548 if the current temperature of the top and bottomplates is less than the temperature limit.

In an embodiment, if one of the plates is at the limit temperature, themethod 510 provides a zero duty cycle to both plate heaters, even thoughone of the plate heaters may be below the temperature limit. Further,the software may be adapted so that if the actual temperature of theplate heater is very close to the limit temperature, the method 510 onlyallows the duty cycle be at or below a predetermined set point. In thismanner, when the actual temperature is very near the limit temperature,the method 510 goes into a fault-type condition and uses a safe dutycycle.

Assuming the actual plate temperatures are below the safe temperaturelimit, the method 510 applies the combined heater duty cycle from theparallel control algorithms at summation point 544. The heater dutycycle applies full power for a certain percentage of a given amount oftime. The given amount of time is the update speed of the fuzzy logiccontrol loop. The fuzzy logic control loop, including the fuzzy logiccontrol algorithm 530, updates about nine times per second in oneembodiment. It should be appreciated that the update rate of the fuzzylogic control loop is an important parameter and that simply increasingthe update rate to a certain value may deteriorate the accuracy of thesystem. One range of update rates that provide good results is fromabout 8.5 times per second to about 9.5 times per second.

The update rate should not be evenly divisible into the frequency of theinput power. For example, an update rate of nine times per second workswhen the AC frequency is held steady at 50 or 60 hertz. However, as isthe case in some countries, the frequency may be 63 hertz. In such acase, an update rate of nine hertz will cause inaccuracy. Therefore, inone embodiment, an update rate of a fraction of 1 hertz is suitable,such as 9.1 hertz. Assuming the update rate to be nine times per second,the time per update is approximately 110 milliseconds. Therefore, if theduty cycle is 0.5, i.e., half on, half off, the time at which full poweris applied is 55 milliseconds. During the other 55 milliseconds, nopower is applied. If the duty cycle is 90%, then full power is appliedfor 90% of 110 milliseconds.

The update speed of the knowledge-based control algorithm 520 is not ascritical as the update speed of the fuzzy logic control loop. For onereason, the signal inputs to the algorithm 520 change gradually overtime so that they do not need to be checked as often as the comparisonbetween the desired fluid temperature and the actual fluid temperature.An update rate of about two seconds is sufficient for the signal inputs.The inputs of the control algorithm 520 can be updated from about onceevery half second to about once every four seconds. The knowledge-basedcontrol algorithm 520 can run on the main processor of the system 10,100, for example, an Intel StrongARM™ Processor. To facilitate theupdate rate of the fuzzy logic control loop, a high speed processor,such as a Motorola Digital Signal Processor is used. The fuzzylogic-based control algorithm 530 runs, in one embodiment, on a delegateprocessor, e.g., a Motorola Digital Processor.

Referring now to FIG. 26, the knowledge-based control algorithm 520 isillustrated in more detail. As discussed above, in a first step, theknowledge-based control algorithm receives a number of signal inputs, asindicated by block 522. Some of these inputs are updated at the mainprocessor level of about once every two seconds. Other inputs are set insoftware as constants. One of the input signals that varies over time,is the number of stroke intervals (“N”) per millisecond. The pump pistonmoves over a certain period of time, stops and dwells, and then movesagain for a certain period of time. The pump makes N number of strokesper millisecond, which is inputted into the knowledge-based controlalgorithm.

Another input signal that varies over time is the input voltage (“Vac”).The input voltage Vac changes over time in a single house or indifferent locations. Another input signal that changes over time is themeasured fluid inlet temperature (“Tin”). Fluid temperature Tin ismeasured by one of the numerous sensors of the method 510 describedabove. An input which will like not change over time is the plate heaterefficiency (“E”). The heater efficiency E is determined empirically. Theheater efficiency E could change depending upon the pressure inside thedisposable unit during heating, the material of the disposable unit andthe gap tolerance between the top and bottom plate. The heaterefficiency E for a particular dialysis device therefore remainssubstantially constant. As described above, the desired fluidtemperature (“Tdesired”) may vary, depending on doctor's orders.However, for any given therapy session, Tdesired is a constant.

The knowledge-based control algorithm 520 calculates a pulsatileflowrate (“Q”) in millimeters per minute according to the formula ofblock 524. The formula for Q can change based on the desired units forthe flowrate. In the illustrated embodiment, the formula for Q is 60,000multiplied by the chamber volume in milliliters, the product of which isdivided by T in milliseconds. Once again, the chamber volume is aconstant that is a function of pump chamber wall geometry.

The knowledge-based control algorithm 520 also calculates the totalheater power in Watts, as indicated by block 526. In the illustratedembodiment, the method 510 calculates the heater power by dividingV_(ac) ² by a plate heater resistance. The knowledge-based controlalgorithm 520 then uses the above calculations to calculate theknowledge-based duty cycle, as indicated by block 528. Theknowledge-based duty cycle equals, in one embodiment, a factor, e.g., of0.07, multiplied by the temperature difference, AT, which equalsT_(desired) minus the T_(in). This product is then multiplied by thepulsatile flowrate Q. The latter product is then divided by the productof the total heater power W times the heater efficiency E. Theknowledge-based duty cycle is then fed into summation point 544 incombination with the fuzzy logic-based duty cycle output as illustratedby FIG. 26.

Referring now to FIG. 27, one embodiment for the fuzzy logic controlalgorithm 530 is illustrated. It should be appreciated that fuzzy logicis known generally to systems engineers and in the field of system andprocess control. The fuzzy logic algorithm described herein is merelyone method of implementing fuzzy logic to perform the task of acceptingan error input, which is the difference between the desired fluidtemperature and the actual fluid temperature, and attempting to minimizethis number to zero. Regardless of the method in which fuzzy logic isemployed, the method inputs a temperature, sums a ΔT, and outputs apower limiter, such as the duty cycle. The first step in the fuzzy logiccontrol logic algorithm 530 is to therefore calculate the differencebetween T_(desired) and T_(in), as indicated by block 532.

Next, a number of membership functions are implemented, as indicated byblock 534. In this embodiment, the algorithm 530 implements fivemeasurement functions. Two of the measurement functions, namely, nlargeand plarge, are trapezoidal membership functions. As is known in the artof fuzzy logic, the trapezoidal membership function consists of fournodes. Three other membership functions, namely nsmall, neutral andpsmall, are set up as triangle membership functions, which consists ofthree nodes. After setting up the membership functions as indicated byblock 534, the fuzzy logic control algorithm 530 performs afuzzification interface as indicated by block 536. In the fuzzificationinterface, the control algorithm 530 converts the temperaturedifference, ΔT, between T_(desired) and T_(in) to a number of fuzzy setsbased on the membership functions set up as indicated in block 534.

Next, the control algorithm 530 applies a number of fuzzy logic heatingrules as indicated by block 538. In an embodiment, the control algorithm530 employs five fuzzy logic rules. One rules says that, if ΔT isnlarge, the output should decrease at a large pace. Another rules saysthat, if ΔT is nsmall, the output should decrease at a small pace. Thethird rule states that if ΔT is neutral, the output should be zero. Afurther rules states that if ΔT is psmall, the output should increase ata small pace. The final rule states that if ΔT is plarge, the outputshould increase at a large pace.

The next step in the fuzzy logic control algorithm 530 is to perform adefuzzification interface, as indicated by block 540. In thedefuzzification interface, the output of the rules is converted to anactual or “crisp” output, which can then be translated into a dutycycle. In the defuzzification step indicated by block 590, the output ofthe fuzzy logic rules is converted to a “crisp” or exact number. Thisnumber is then converted to the proper output for the heater which, inthis embodiment, is the fuzzy heater duty cycle.

As indicated by block 542, the next step is to determine how much weightto place on the fuzzy logic duty cycle with respect to theknowledge-based duty cycle. The weighting factor is decided by the fuzzylogic rules and the update rates of both the knowledge based and fuzzylogic based control algorithms. The weighted fuzzy logic duty cycle isthen summed in summation point 544 with the knowledge-based duty cycleyielded by the knowledge-based control algorithm 520.

IX. Electrical Insulation for the System

Medical equipment and in particular equipment in intimate contact with apatient needs to be properly electrically insulated against leakagecurrents. Class I type of equipment provides basic insulation and ameans of connecting to a protective earthing conductor in the buildingin which the equipment resides, which dissipates hazardous voltages ifthe equipment insulation fails. One primary use for the system 10, 100of the present disclosure however is in a patient's home. This presentstwo problems for Class I devices and in particular for dialysismachines. First, in many countries and older homes, the earthing groundis faulty, unreliable or completely absent. Second, many people bypassgrounding systems that do exist. The present disclosure overcomes thisproblem by providing an automated dialysis system 10, 100 that requiresno earth ground. The system 10, 100 does not simply rely on the basicinsulation provided by Class I devices but provides either doubleinsulation or reinforced insulation.

Double insulation includes two layers of insulation. One layer ofinsulation can be the basic insulation. At 240 VAC, basic insulationtypically requires four millimeters of “creepage” or 2.5 millimeters of“air clearance”. Creepage is the shortest distance between twoconductive parts when both are disposed along a surface of insulation.Creepage is also the shortest distance between a conductive part and abounding surface of a piece of equipment, wherein the conductive partand the equipment contact a piece of insulation. Air clearance is theshortest distance between two conductive parts or between a conductivepart and a piece of equipment, measured through air.

The additional layer of insulation is called supplemental insulation.Supplemental insulation is independent insulation applied in addition tothe basic insulation to ensure protection against electric shock if thebasic insulation fails. The supplemental insulation can also be in theform of creepage and clearance.

Reinforced insulation, on the other hand, is a single layer ofinsulation offering the same degree of protection as double insulation.Reinforced insulation provides the electrical protection equivalent todouble insulation for the rated voltage of the double insulation. For240 VAC, used as the mains voltage of the system 10, 100, the basicinsulation can withstand 1500 VAC and the supplemental insulation canwithstand 2500 VAC. The single layer of reinforced insulation musttherefore withstand at least 4000 VAC.

Referring now to FIG. 28, one embodiment of an electrically insulatedsystem 550 of the present disclosure is illustrated. The system 550 isillustrated schematically, however, certain components of the system 550are identifiable as components illustrated in the hardware drawingsdiscussed above. For example, the system 550 includes the housing orenclosure 112, illustrated above in FIGS. 3A to 4B, which includes thebase 114 and the lid 116 of the hardware unit 110. The system 550 alsoincludes the heater 16, which in an embodiment includes upper and lowerheating plates illustrated in FIG. 3A and discussed in connection withFIGS. 25 to 27. Further, the system 550 includes the display device 40and temperature sensors 62 illustrated and discussed in connection withFIGS. 1 and 2.

In FIG. 28, the numbers in parenthesis indicate the working or operatingvoltage of the respective component. As illustrated, the line 552 andneutral 554 supply a mains voltage of 240 VAC, single phase, in anembodiment, which is the standard voltage used residentially in manycountries throughout the world. The line 552 and neutral 554 couldotherwise supply the United States residential standard of 120 VAC,single phase, and indeed could provide a voltage anywhere in the rangeof 90 to 260 VAC. The line 552 and neutral 554 feed the 240 VAC into amains part 556. It is worth noting that the system 550 does not includeor provide a protective earth conductor.

The mains part 556 feeds 240 VAC to a power supply printed circuit board(“PCB”) 558. Power supply PCB 558 includes a mains part 562 and a livepart 564. For purposes of the present disclosure, a “mains part” is theentirety of all parts of a piece of equipment intended to have aconductive connection with the supply mains voltage. A “live part” isany part that if a connection is made to the part, the part can cause acurrent exceeding the allowable leakage current for the part concernedto flow from that part to earth or from that part to an accessible partof the same equipment.

As illustrated, the live parts 560 and 564 step down in voltage from themains parts 556 and 562, respectively, to 24 VDC. Obviously, the voltagemay be stepped down to other desired levels. Live part 560 feeds livepart 566. Live part 566 is an inverter having a step-up transformer thatoutputs a voltage of 1200 Vpeak. The inverter 566 powers a number ofcathode fluorescent lights, which provide backlighting for the displaydevice 40.

Live part 560 is also electrically isolated from applied part 568, whichis maintained at a zero potential. An “applied part” for purposes of thepresent disclosure is any part of the system 550 that: (i) comes intophysical contact with the patient or operator performing the dialysistreatment; (ii) can be brought into contact with the patient oroperator; or (iii) needs to be touched by the patient. For instance, itis possible for the patient to touch the upper or lower plates of theplate heater 16, the temperature sensors 62 and the enclosure or housing112. The applied part 568 represents schematically the casing orinsulation around the temperature sensors 62.

In an embodiment, which only includes a display device 40 and not atouch screen 42 (discussed in FIGS. 1 and 2), the housing 112 includes awindow 570, such as a glass or clear plastic window. The glass orplastic window provides the same level of insulation as the rest of the,e.g., plastic housing or enclosure 112. In an embodiment which doesinclude a touch screen 42, the touch screen is properly electricallyinsulated, preferably by the manufacturer of same. Alternatively, one ormore layers of insulation discussed below could be added to system 550to properly insulate the touch screen 42.

The system 550 makes available an input/output port 572, which can be aserial port or an Ethernet port to connect the system 550 to an externalcomputer, a local area network, a wide area network, an internet and thelike. To electrically insulate input/output port 572, the systemprovides a protective covering or casing 574.

The mains part 556 powers the heater element 576, which is positionedand arranged to heat both the upper and lower plates of the plate heater16. In an alternative embodiment (not illustrated), the mains part 556powers the infrared heater discussed above. As illustrated, doubleinsulation is maintained between the heater element 576 and the heaterplate 16. The double insulation includes basic insulation B(240), ratedfor 240 VAC, and supplemental insulation S(240), rated for 240 VAC.

For the heater plate 16 and element 576, at least, the basic andsupplemental insulation needs to be electrically insulative butthermally conductive. Polyimides, such as a Kapton®, work very well. Inan embodiment, therefore, the B(240) and S(240) layers each includeKapton® tape or sheet of about 0.3 millimeters thickness. As furtherillustrated, another layer of basic insulation B(240), rated for 240VAC, and another layer of supplemental insulation S(240), rated for 240VAC, are disposed between the temperature sensor 62 and the heater plate16. Thus the heater plate 16 is completely and doubly insulated from theremainder of the system 550. Alternatively, either of the double layersof insulation can be replaced by a single layer of reinforcedinsulation.

The line 552 and the neutral 554 are insulated by basic operationinsulation BOP (240), rated for 240 VAC, which is the electricalinsulation wrapped or extruded around the respective wires. Basicinsulation B(240), rated for 240 VAC, is provided between the mains part556 and the enclosure 112 and between the power supply PCB 558 and theenclosure. The basic insulation B(240) can be in the form of a properlyseparated air gap. The enclosure 112 itself provides supplementalinsulation S(240) for 240 VAC. The mains part 556 is therefore doublyinsulated from the outside of the enclosure 112.

Since applied part 568 is maintained at a zero operating voltage, thereneeds to be no additional insulation placed between the applied part 568and the housing 112. Accordingly, there is simply an operationalseparation displayed figuratively as OP between the applied part 568 andthe housing 112. Double insulation or reinforced insulation D/R (24) for24 VDC is however provided between live part 560 and the applied part568, so that applied part 568 maintains its zero potential. Basicinsulation B(24), rated for 24 VDC, is provided between live part 560and the enclosure 112. The basic insulation B(24) can be in the form ofa properly separated air gap. As stated above, the enclosure 112 itselfprovides supplemental insulation S(240) for 240 VAC. Live part 560 istherefore doubly insulated from the outside of the enclosure 112.

No additional insulation is needed and only an operational separation OPis provided between live part 560 and the live part 566. Since live part566 is stepped up to 1200 Vpeak, the supplemental insulation S(240)rated for only 240 VAC of the enclosure 112 should not be relied upon.Accordingly, double insulation or reinforced insulation D/R (1200) for1200 Vpeak is provided between the live part 566 and the housing 112.

Double insulation or reinforced insulation D/R (240) for 240 VAC isprovided between the mains part 556 and the live part 560. Doubleinsulation or reinforced insulation D/R (240) for 240 VAC is alsoprovided between the line and neutral line 554 and the upper and lowerplates of plate heater 16. Still further, double insulation orreinforced insulation D/R (240) for 240 VAC is provided between themains part 562 and the live part 564 of the power supply PCB 558. Here,in the case of double insulation, either the basic or supplementaryinsulation can be a properly separated creepage distance on the PCB 558.

Double insulation or reinforced insulation D/R (24) for 24 VDC isprovided between the housing 112 and the display device 40. Theseparation between the display device 40, maintained at 24 VDC and theinverter, maintained at 1200 Vpeak is only required to be operational.Live part 566 must be separated from the outside of the housing 112 byD/R(1200) but not from the LP(24). The reason is that the LP(1200) is onthe secondary side of the live part 566 and if it is shorted to theLP(24) due to a failure of the operational insulation, LP(1200) willbecome at most 24 VDC, providing no safety hazard.

X. Graphical User Interface

Referring now to FIG. 29, one embodiment of a graphical user interface(“GUI”) system 600 is illustrated. The GUI system 600 in an embodimentemploys web-based software as well as other types of software. Asdiscussed previously in connection with FIG. 28, the system 10, 100 ofthe present disclosure is provided with an input/output (e.g., serial orEthernet) port 572, which is normally insulated from the patient by acover 574. The port 572 allows the controller 30 of the system 10, 100to access an internet and a variety of other networks. The GUI system600 of the present disclosure takes advantage of this capability byenabling the controller 30 to interact with software on an internet orother network.

It should be appreciated that the GUI system 600 does not require thepatient to have internet or network access in their home. Rather, theport 572 is for a maintenance person or installer to gain access to thecontroller 30 within the hardware unit 110. In this manner, the patientmay bring their unit to a place having internet or network access,wherein the patient's software may be upgraded. The patient may thenbring the unit home and operate it without having to gain internet ornetwork access.

Using web-based software is advantageous because it is based on wellestablished standards, so that the interface screens may be constructedusing existing software components as opposed to being hand crafted.Web-based software allows for external communication and multiple accesspoints. The software is portable. For each of these reasons, softwareconstructed using existing software components reduces development timeand cost.

The present disclosure includes the construction of a GUI using anembedded web browser 602. In an embodiment, the embedded web browser 602is third party software. The embedded web browser 602 can include anythird party browser that runs on a target platform and includes supportfor advanced features such as HTML 4.0, ECMAScript, and animated GIFs.The web browser 602 renders and supplies the various GUI screens to thevideo monitor 40. The web browser 602 also handles inputs made by thepatient. When the operator interacts with the system (e.g., pressesbuttons 43, 124, 125 and 127 or turns knob 122, illustrated in FIG. 3B),the web browser 602 forwards information about the interaction to theembedded web server 604.

The web server 604 in turn uses a web server extension software 606 toprocess the interaction. The embedded web server 604 can also be anythird party web server that runs on a target platform and includessupport for the web server extension software 606 and that allows adynamic definition of the information to be sent to the embedded webbrowser 602.

The web server extensions are developed internally using the web serverextension software 606 and conform to the specification of a mechanism,such as a Servlet, which works in conjunction with the chosen embeddedweb server 604. The web server extension software 606 enables the webserver 604 to retrieve back end and real time information from theinstrument access and control software 608. There are a number ofdifferent existing web server extension technologies that may be usedfor the embedded web browser 602, the embedded web server 604 and theweb server extension software 606, such as CGI, ASP, Servlets or JavaServer Pages (“JSP”).

The web server extension software 606 interacts with the instrumentaccess and control software 608. The instrument access and controlsoftware 608 is an internally developed operating environment forcontrolling the various lower level components of the system 10, 100,such as the valve motor/actuator, pump motor/actuator and heater.

Depending on the operator input and the state of the automated dialysissystem 10, 100, the web server extension software 606 can interact withthe instrument access and control software 608 to obtain informationfrom same and to cause one of the devices of the system 10, 100 to takeaction. The web server extension software 606 then sends information tothe embedded web browser 602, which may then be displayed on the displaydevice 40. The web server extension software 606 communicates with theinstrument access and control software 608 using, in an embodiment, theCORBA standard. This communication, however, may take place usingvarious different protocols known to those of skill in the art.

During the operation of the system 10, 100, an event may occur thatrequires high priority information to be displayed to the operator, forexample, an alarm and corresponding message either on the display device40 or on a separate dedicated alarm display. When a high priority eventoccurs, the instrument access and control software 608 generates anevent that is handled by an event-handling software 610, which can bedeveloped internally. The event-handing software 610 in turn notifiesthe embedded web browser 602, through the use of a plug-in or a refreshrequest simulation from the web server 604, to refresh whatever displaythe web browser is currently causing to be displayed on display device40.

The event-handing software 610 enables information to flow from theinstrument access and control software 608 to the embedded web browser602 without a request by the embedded web browser 602, wherein the webbrowser thereafter requests a refresh. The web server 604 then forwardsthe request to the web server extension software 606. The web serverextension software 606 determines what information should be displayedon the display device 40 based on the state of the system 10, 110. Theweb server extension software 606 then relays that information back tothe embedded web browser 602, which updates the display device, e.g., toshow an alarm condition.

In one embodiment of the GUI system 600, the web client is internal tothe hardware unit 110 of the system 10, 100. As described above inconnection with FIG. 1, the controller 10 includes a plurality ofprocessors (referred to collectively herein as processor 34). A mainmicroprocessor is provided that resides over a number of delegateprocessors. Each of the embedded web browser 602, web server 604, webserver extension software 606 and event handling software 610 run on themain microprocessor. The instrument access and control software 608 runson the main microprocessor and one or more of the delegate processors.

It is alternatively possible that a number of different external webclients may need to access information contained within the system 10,100. It is therefore preferred that the HTTP commands to the embeddedweb server 604 not require predetermined passwords, but instead use astronger and more flexible security system.

Referring now to FIGS. 30A-30M, a number of screen shots of the GUI 600are illustrated that show the overall look and feel of the system 10,100 as seen by the operator or patient. Further, these drawingsillustrate various features provided by the GUI system 600. The goal ofthe automated dialysis system of the present disclosure is to make asimple and well operating system. The device only requires two supplybags 14, weighs less than 10 kg and can be powered virtually anywhere inthe world without the risk of electrical shock to the patient.Similarly, the GUI system 600 is designed to be simple, intuitive,effective, repeatable and reliable.

As illustrated in FIG. 3B, the system 10, 100 includes a display device40, a knob 122 that enables the user to interact with the GUI system 600and a number of dedicated pushbuttons 43 that enable the patient tonavigate between three different screens namely a parameter changescreen, a log screen and a therapy screen. In an embodiment, a displaydevice 40 is provided, wherein the input devices 43, 122, 124, 125 and127 are each electromechanical. In an alternative embodiment, one ormore of the input devices are provided by a touch screen 42 thatoperates with the display device 40 and a video controller 38.

A simulated or electromechanical “stop” input 124, an “OK” button 125and a “back” button 127 are also provided. The OK button 125 enables theoperator to indicate that a particular part of the set-up procedure hasbeen completed and to prompt the GUI 600 to move on to a next step ofthe set-up stage or to the therapy stage. The stop button 124 enablesthe operator or patient to stop the set-up or therapy procedures. Thesystem 600 may include a handshake type of response, such as “are yousure you want to stop the set-up”. Other parts of the entire procedure,such as the patient fill or drain cycles immediately stop withoutfurther input from the operator. At certain points in the procedure, thesystem enables the operator to move back one or more screens using theback button 127.

Referring now to FIG. 30A, the display device 40 and the videocontroller 38 are adaptable to display animations, which provide thepatient with information and instructions 612 in a comfortable format.As illustrated throughout the screen shots, the GUI system 600 waits forthe patient to read and understand whatever is being displayed on thedisplay device 40 before moving on to the next step or stage. FIG. 30Aillustrates that the GUI system 600 is waiting until the patient isready before beginning the therapy. The system 600 prompts the user topress an “OK” input to begin the therapy. FIG. 30A also illustrates thatthe therapy screen is being presently displayed by highlighting the word“therapy” at 614.

In FIG. 30B, the display device 40 of the GUI system 600 prompts thepatient to gather the necessary supplies for the therapy, such as thesupply bags 14. FIGS. 30B and 30C illustrate that the system 600 usesstatic images, such as static image 616 and animations, such asanimation 618, which resemble the actual corresponding supplies or partsto aid the patient in easily, effectively and safely connecting to thesystem 10, 100. For example, the animation 618 of FIG. 30C looks likethe actual hose clamp of the system 10, 100, which aids the patient infinding the proper piece of equipment to proceed with the therapy. Thearrow of the animation 618 also illustrates the action that the patientis supposed to perform, reducing the risk that the patient willimproperly maneuver the clamp or perhaps break the clamp.

FIGS. 30D and 30E illustrate that the GUI system 600 promotes hygienicoperation of the system 10, 100 by prompting the patient to: (i) takethe steps of covering the patient's mouth and nose at the proper time;and (ii) wash the patient's hands before coming into contact withcritical fluid connectors, such as the patient fluid connector and thesupply bag connectors. The GUI system 600 waits for the patient tofinish and press an OK input at each step before proceeding to the nextstep. As illustrated in FIGS. 30D and 30E, software LEDs 620 located atthe top of the display device 40 indicate where the user is in theset-up procedure.

Screen shots of FIGS. 30A to 30E and 30H to 30M each present proceduralset-up steps of the therapy. Accordingly, the colors of the screen shotsof FIGS. 30A to 30E and 30H to 30M are chosen so that they are morevisible when viewed during the day or with lights on. In one embodiment,the screens are different shades of blue, wherein the static images andanimations and inner lettering are white and the outer lettering andborders are black. As illustrated by FIGS. 30F and 30G however, thescreen shots that illustrate the active stages of the therapy are chosenso that they are more visible when viewed at night or with lights off.In one embodiment, the screen shots of FIGS. 30A to 30F are black withruby red lettering, diagrams and illustrations, etc. The red letting isconfigured so as not to be intrusive to a sleeping patient but stillvisible at distances of about 10 to 25 feet (3 to 7.6 meters).

FIGS. 30F and 30G illustrate that during active stages of the therapy,the therapy status information is displayed on the screen shots in theform of both graphics 622 and numerical data 624. Therapy statusinformation is displayed in real time or in substantially real time witha slight time delay. FIG. 30F illustrates a screen shot during a fillportion of the therapy. In particular, FIG. 30F illustrates the firstfill of three total fills. The graphical clock 622 illustrates that thefill cycle time is approximately ⅛th elapsed. The arrow graphic 622indicates that the therapy is in a fill cycle. Also the graphicalrepresentation of the body 622 has a very low percentage of dialysate.The numerical data 624 illustrates that the system 10, 100 has pumped150 ml of dialysate into the patient.

FIG. 3G illustrates that the patient is currently undergoing the firstdrain cycle of three drain cycles that will take place overnight. Thegraphical representation of the clock illustrates that the drain cycletime is approximately ⅛th elapsed. The graphical arrow is pointingdownward indicating a drain cycle. The body is shown as beingsubstantially full of dialysate. The numerical data 624 illustrates that50 ml of dialysate has been removed from the patient.

FIGS. 30H and 30I illustrate that in the morning when the therapy iscomplete, the screen reverts back to the daytime colors, or colors whichare more easily seen in a lighted room. FIG. 30H includes informationand instructions 612 that prompt the patient to disconnect from thesystem 10, 100. The system waits for the patient to select the OK button125 (FIG. 3B) before proceeding. FIG. 30I includes an animation 618,which illustrates an action and equipment that the patient whiledisconnecting from the system. For each action in the disconnectionsequence, system 600 waits for the patient to select the OK button 125(FIG. 3B) before proceeding.

FIGS. 30J to 30M illustrate that in an embodiment, the user navigatesbetween the therapy, parameter changes and log information by selectingone of the dedicated inputs 43 illustrated in FIG. 3B. FIG. 30Jillustrates that the patient has selected the input 43 associated withthe parameter changes information. The screen 40 in FIG. 30J nowhighlights the word “changes” instead of the word “therapy.”

The parameter screen presents parameter information to the patient in ahierarchy format. First, as in FIG. 30J, the system 600 presentscategories 625 of parameters, such as patient preferences, daily patientdata, therapy parameters, nurse parameters and service parameters. Thepatient can scroll through the various categories 625 using theadjustment knob 122 of FIG. 3B, so that a desired category 625 isdisplayed in a highlighted display area 626. FIG. 30H illustrates thatthe patient preferences category 625 is currently displayed in thehighlighted display area 626.

Once the user selects a highlighted category 625 by pressing the OKbutton 125 (FIG. 3B), a first door 628 slides open and presents the userwith a list of the parameters 627 for the selected category 625 (e.g.,the patient preferences category), as illustrated by the screen 40 ofFIG. 30K. FIG. 30K illustrates that the patient preferences category 625is displayed above the door 628, so that the patient knows whichcategory 625 of parameters 627 is being displayed. At the same time, thehighlighted display area 626 now displays one of a select group of theparameters 627 belonging to the patient preferences category 625.

The parameters 627 illustrated in FIG. 30K as belonging to the patientpreferences category 625 include a display brightness percent, a speakervolume percent and a dialysate temperature in degree Celsius. Obviously,the patient preferences category 625 may include other parameters 627.The other categories 625 illustrated in FIG. 30J include differentparameters 627 than those illustrated in FIG. 30K.

The patient can scroll through and select one of the parameters 627 forthe patient preferences category 625 by rotating knob 122. In thismanner, it should be appreciated that the signal knob 122 is used overand over again. This feature is in accordance with the goal of providinga simple system, wherein the patient only has to turn one knob insteadof remembering which knob from a plurality of knobs applies to aparticular feature. The knob 122 also enables the lettering to be biggerbecause the patient can scroll through to see additional parameterselections that are not displayed when the door 628 is initiallydisplayed. That is, the functionality of the knob 122 provides freedomto the GUI 600 to not have to display all the possible parameters atonce. It should be appreciated that this benefit also applies to thecategory selection screen of FIG. 30J, wherein each of the categories625 does not have to be displayed simultaneously.

Once the patient selects one of the parameters of the patientpreferences category, e.g., by pressing the OK button 125, a second door630 slides open, wherein the display device 40 illustrates that thepatient has selected the display brightness parameter 627 of the patientpreferences category 625, which is still displayed by the first door 628in FIG. 30L. The highlighted area 626 now displays one of the range ofpossible values 632 for the selected parameter 627 of the selectedcategory.

In FIG. 30L display device 40 illustrates that the highlighted displayarea 626 currently shows a value 632 of eighty for the displaybrightness parameter 627 of the patient preferences category. Onceagain, the patient changes the value 632 of the selected parameter 627by rotating the knob 122. When the patient selects a value 632 (bypressing the OK input 125 illustrated in FIG. 3B while the desired valueis displayed) for the parameter of the chosen category, the GUI system600 saves the value as indicated by the display device 40 in FIG. 30M.FIG. 30M illustrates that the system 600 provides a feedback message tothe patient that the selected value has been saved.

The system 600 in an embodiment presents information and instructions tothe operator through the various visual tools discussed above. In analternative embodiment, in addition to the visual information andinstructions 612, static images 616, animations 618, parameterinformation, etc., one, or more or all of the above disclosed methods ofcommunication is presented audibly to the patient or operator throughspeakers 129 (FIG. 3B) and a sound card (not illustrated) that cooperatewith the controller 30 of the system 10, 100.

The various programs that run on the main microprocessor can alsoinclude one or more programs that activate a certain sound file at acertain time during the therapy or upon a certain event initiated by thesystem 600, e.g., an alarm, or upon a patient or operator input. Thesound files can contain the sound of a human voice or any other type ofsound. The sound files walk the patient through the set-up portion ofthe therapy in an embodiment. The sound files can alert a patient whohas made an inappropriate input into the GUI 600, etc. The system doesnot activate a sound during the cycles, e.g., while the patient sleeps,in an embodiment.

If the operator selects the dedicated input 43 corresponding to the loginformation (not illustrated), the GUI 600 displays a screen or screensthat show therapy data. In an embodiment, the therapy data is presentedin a number of operator selectable logs. One of the logs can be adefault log that is displayed initially, wherein the operator can switchto another log via, e.g., the knob 122. The logs may pertain to the mostrecent therapy and/or can store data over a number of days and a numberof therapies. The logs can store any type of operating parameterinformation such as cycle times, number of cycles, fluid volumedelivered, fluid temperature information, fluid pressure information,concentration of dialysate constituents, any unusual or alarm type ofevents, etc.

It should be understood that various changes and modifications to thepresently preferred embodiments described herein will be apparent tothose skilled in the art. Such changes and modifications can be madewithout departing from the spirit and scope of the present invention andwithout diminishing its intended advantages. It is therefore intendedthat such changes and modifications be covered by the appended claims.

The invention is claimed as follows:
 1. A peritoneal dialysis systemcomprising: an enclosure; a stepper motor housed by the enclosure; asolid pump piston including a solid piston shaft attached to orintegrally formed with a solid pump head, the solid pump piston inoperable communication with the stepper motor; a disposable unitincluding at least one flexible membrane attached to a rigid piece, theenclosure and the disposable unit structured and arranged to allow theflexible membrane to move beyond a relaxed position of the flexiblemembrane, the enclosure structured and arranged to receive thedisposable unit such that the stepper motor can move the solid pump headtowards and away from the disposable unit to allow (i) the flexiblemembrane to move outwardly from the rigid piece as the solid pump headis moved away from the disposable unit, and (ii) the flexible membraneto move within the rigid piece as the solid pump head is moved towardsthe disposable unit; and an encoder operable with the stepper motor, theencoder configured to provide an output indicative of a position of thesolid pump head after the solid pump head has moved towards or away fromthe disposable unit.
 2. The peritoneal dialysis system of claim 1, whichincludes a controller configured to receive the output from the encoderto indicate the position of the solid pump head after the solid pumphead has moved towards or away from the disposable unit.
 3. Theperitoneal dialysis system of claim 1, which includes a ball screw inoperable communication with the stepper motor and the solid pump head,the ball screw operable to convert a rotational output of the steppermotor to a translational motion of the solid pump head.
 4. Theperitoneal dialysis system of claim 1, wherein the encoder includes alinear encoder.
 5. The peritoneal dialysis system of claim 1, whereinthe encoder is configured to provide information indicative of aposition of the solid pump head after a power loss.
 6. The peritonealdialysis system of claim 1, wherein the encoder is configured to provideinformation indicative of how far from a home position the solid pumphead has traveled.
 7. The peritoneal dialysis system of claim 6, whereinthe home position is a zero degree position for the encoder.
 8. Theperitoneal dialysis system of claim 1, which includes a pneumaticsource, wherein the enclosure is structured and arranged to allow anegative pressure from the pneumatic source to be applied to theflexible membrane of the disposable unit.
 9. The peritoneal dialysissystem of claim 1, wherein the rigid piece and the at least one membranedefine at least one of a valve portion or a pump portion of thedisposable unit.
 10. A peritoneal dialysis system comprising: anenclosure; a door hingedly attached to the enclosure; a stepper motorhoused by the enclosure; a solid pump piston including a solid pumpshaft attached to or integrally formed with a solid pump head, the solidpump piston in operable communication with the stepper motor; adisposable unit contacting the enclosure and the door, the disposableunit including a moveable membrane operable with the solid pump head,the stepper motor configured to move the solid pump head towards andaway from the disposable unit; and a position detection apparatusoperable with the stepper motor and located to provide an outputindicative of a position of the solid pump head relative to a referenceposition.
 11. The peritoneal dialysis system of claim 10, which includesa controller configured to receive the output from the positiondetection apparatus to indicate the position of the solid pump headrelative to the reference position.
 12. The peritoneal dialysis systemof claim 10, which is configured such that the moveable membrane of thedisposable unit moves with the solid pump head as the solid pump head ismoved towards or away from the disposable unit.
 13. The peritonealdialysis system of claim 10, wherein the position detection apparatusenables the position of the solid pump head to be known upon power-up ofthe peritoneal dialysis system.
 14. The peritoneal dialysis system ofclaim 10, wherein the position detection apparatus includes an encoder,a proximity sensor, a magnetic pick-up, or a combination thereof. 15.The peritoneal dialysis system of claim 10, which is operable with abattery back-up to power at least the position detection apparatus. 16.The peritoneal dialysis system of claim 10, wherein the referenceposition is a fully opened or fully closed position of the moveablemembrane of the disposable unit.
 17. The peritoneal dialysis system ofclaim 10, which is configured to move the solid pump head automaticallyuntil the reference position is sensed by the position detectionapparatus.
 18. A peritoneal dialysis system comprising: an enclosure; adoor hingedly attached to the enclosure; a stepper motor housed by theenclosure; a solid pump piston including a solid piston shaft attachedto or integrally formed with a solid pump head, the solid pump piston inoperable communication with the stepper motor; a disposable unitoperable with the enclosure and the door, the disposable unit includinga moveable membrane operable with the solid pump head, the stepper motorconfigured to move the solid pump head towards and away from thedisposable unit; and a position detection apparatus located to providean output indicative of a position of the solid pump head relative to areference position, and wherein the peritoneal dialysis system isprogrammed to move the solid pump head automatically until the referenceposition is sensed.
 19. The peritoneal dialysis system of claim 18,wherein the stepper motor is programmed to control at least one of (i)velocity of the stepper motor, or (ii) acceleration of the stepper motorfor controlling the pressure of fluid to be pumped by the solid pumppiston.
 20. The peritoneal dialysis system of claim 18, wherein thestepper motor is programmed to include at least one of (i) a presetvelocity for the stepper motor, or (ii) a preset acceleration for thestepper motor.
 21. The peritoneal dialysis system of claim 18, whichincludes a pump chamber, and which is configured to control a pressurewithin the pump chamber by controlling the velocity of the steppermotor.
 22. The peritoneal dialysis system of claim 18, wherein theposition detection apparatus includes an encoder.
 23. The peritonealdialysis system of claim 18, which is configured to move the solid pumppiston automatically upon power-up until the reference position issensed.